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User's Guide

The History of the U.S. Census

"Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons. The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct."
Constitution Article 1 Section 2
The first census (under the direction of Secretary of State Thomas Jefferson) was taken in 1790 by 16 federal marshals (one for each colony and the three territories). Field marshals of the U.S. judicial districts were the field supervisors for the first nine censuses (through 1870), while deputy marshals served as the enumerators.
As 95% of our population at that time lived in rural areas (often with little or no access), collecting the information was quite difficult for the marshals. Often they had to use word-of-mouth to learn of households out in the country. Additional problems included lack of cooperation due to suspicion of the questions, for various reasons. Some of the marshals were tarred and feathered. This nine-month task took 18 months. The final tabulation in March 1792 counted 3,929,326 in the United States. As seen in the Constitution excerpt at the top of the article, this count excluded Indians not taxed, and counted slaves as three-fifths of a free person. When Jefferson sent a copy of this final count to President Washington (the original census lists can be seen on microfilm at the National Archives), they both agreed that the count was incomplete. Jefferson's estimate of the actual population was close to 4,100,000. Blame was placed on citizens for lack of cooperation (many thought the purpose of the census was for taxation), and also on some of the enumerators (census-takers) for laziness. On the whole, they felt that this census was a success, and proof to the European countries of the importance of this new nation.
This first census of 1790 included more than just the number of free people and slaves. It also included the sex of free persons, as well as who was the head of the household, and the age of white males over 16. To some in Congress, this first census was felt to be a great opportunity that was wasted. They wanted to be able to collect much more information on this new nation to help determine how best to govern the people. James Madison (father of our Constitution) proposed to include the occupation of all those employed, as well as the age of all free people. However, some others in Congress felt this to be ineffective on a cost basis. And still others felt all this information gathering to be an invasion of privacy to its citizens. This debate being unresolved, the second census, taken in 1800, asked the same questions as the first.
Soon, however, others came around to Madison's point of view. The next census in 1810 (when Madison was president) began to collect additional information. A census of manufactures began with the 1810 census. In 1850, a change was made from taking the name of just the head of the household, to recording every person's name, along with their age, martial status, race or nationality. As the country was in the midst of the first great wave of immigration, these statistics were later used to determine immigration quotas, something our founding fathers had never envisioned.Beginning in 1880, census supervisors were appointed to each census district to be responsible for the enumeration. The temporary field offices that had been used were tossed in favor of a census office. This was the genesis of the census practices that are used today. In 1890, a new machine was used to help in the taking of the census. The year before, Herman Hollerith, a Census Bureau employee, developed the Hollerith Electric Tabulating Machine, using punch holes in cards to record the information. Hollerith later used this invention to start his own company, which later became known as International Business Machines (IBM). In 1902, Congress enacted the Permanent Census Act, which created the Bureau of the Census.
In addition to the Hollerith invention, the Census Bureau has implemented many other improvements to conducting the task of the various censuses. The development of sampling techniques early in the 20th century made it possible, beginning with the 1940 census, to ask some of the census questions of 5 percent of the population to yield reliable estimates for most of the 1940 census areas. Thereafter, the proportion of the households included in the sample varied from one census to the next. In 1970, several questionnaires were used, resulting in three separate samples - 5%, 15% and 20%. In 1990, and again for Census 2000, the sample questions were asked of every sixth household. In places with less than 2,500 inhabitants, every second household was sampled, while more heavily populated areas were sampled at either a 1-in-6 or a 1-in-8 rate.
A major change in how the census is conducted was made in 1960. For the first time, questionnaires were mailed out to households, with the instructions to fill them out and held until an enumerator picked them up. This was called self-enumeration. The thinking was that with more time to fill out the survey, greater accuracy would be achieved. This would also save time and money, as the enumerator would be taking the time to help only those who needed it. This process worked so well that the Census Bureau changed to a mail-out/mail-back system in 1970. Enumerators would now only be needed for those who did not fill out the questionnaire, or those who needed help. For Census 2000, approximately 95 percent of the households received and were asked to return questionnaires in the mail. For households that received a questionnaire in the mail, enumerators telephoned or visited only in those cases where the questionnaires were not returned, the data were incomplete, or where information was needed for people living in institutions, dormitories, or other such quarters. There also were special procedures for enumerating the homeless, people on maritime vessels, and members of the Armed Forces. In a few remote or sparsely populated areas, enumerators visited each housing unit and completed a short-form or long-form census questionnaire.
The principal topics listed below indicate how the range of the population censuses grew during the past two centuries:
  • Age and sex, 1790-present (but only for free Whites until 1820)
  • Slave status, 1790-1860
  • Color or race, 1790-present (see section below)
  • Citizenship, 1820-1830,1870, 1890-present
  • Physical or mental handicap, 1830-1930,1970-present
  • Education or literacy, 1840 present
  • Marital status, 1880-present
  • Occupation, 1850-present
  • Industry, 1820,1840,1910-present
  • Employment status, 1880-present (except 1920)
  • Crime, 1850-1910
  • Mortality, 1850-1890
  • Place of birth, 1850-present
  • Wage rates, 1850-1890
  • Income, 1940-present
  • Pauperism, 1850-1860,1880-1890, 1910
  • Prisoners, 1880-1910
  • Institutionalized persons, 1880-1890, 1910
  • Year of immigration, 1890-1930, 1970-present
  • Number of children ever born, 1890-1910, 1940-1990
  • Language (or whether the person could speak English), 1890-1940, 1960-present
  • Language of parents, 1910-1920
  • Spanish/Hispanic origin or descent, 1970-present
In the 20th century, interest focused as well on people's economic characteristics - their jobs and how they traveled to work, their income, and how well they were housed. Most of these questions have continued to be asked on a sample basis.
The concept of color or race in the censuses has never denoted any scientific definition of biological stock. "White "and "Black "persons have been identified in every decennial census since 1790. American Indians were first enumerated as a separate group in the 1870 census; however, until 1890, those in the Indian Territory or on reservations were not included in the official U.S. population count used for congressional apportionment. Data have been collected on the Chinese population since the 1870 census, and on the Japanese beginning in 1890. Until recently, the census taker determined a person 's color or race according to the Census Bureau 's guidelines. Beginning with the 1960 census, however, respondents who completed their own census questionnaires were able to classify themselves and other household members. Census 2000 made provision for each person 's race to be marked as White, Black, African American, or Negro, American Indian or Alaska Native, Asian Indian, Japanese, Chinese, Filipino, Hawaiian, Korean, Vietnamese, Guamanian or Chamorro, Samoan, or to be written in if none of these applied. In addition, American Indians were asked to report their tribe. The Hispanic population, which the Census Bureau recognizes as an ethnic group, now is identified primarily by a question on Hispanic origin or descent (Mexican, Mexican American, or Chicano, Puerto Rican, Cuban, or other Spanish/ Hispanic/Latino), although other measurements are also available in terms of language spoken at home. Prior to Census 2000, respondents were asked to select only one category when identifying their racial group. With the Office of Management and Budget 's (OMB) decision in July 1998 to revise its standards for the classification of Federal data on race and ethnicity (according to Directive 15), however, the Census 2000 questionnaire allowed the respondent to mark one or more races depending on what that person considered himself/herself to be.
To learn more about the history of the United States Census, view the document put out by the U.S. Census Bureau entitled "Measuring America: The Decennial Censuses from 1790 to 2000"


The law requires that the Census Bureau release the final population counts by State by the end of the calendar year in which the census is conducted. This release allows for the determination of the number of Congressional seats that will be allocated to each State. The next legal deadline is April 1, one year after the Census is conducted, when population counts by age (18 and over), race and ethnicity must be released to the census block level for states to begin the process of redistricting their allotted congressional districts to comply with the one person/one vote requirement.
Once the deadlines are met, the Census Bureau begins to release the full range of decennial producets. The majority of scheduled products are released over the following three years. The following sections of the census users guide detail some of the changes from previous censuses and highlight the key data categories.
Many data subjects found in the 2000 Census can also be found in the 1990 and previous censuses. However, caution must always be used when examining temporal changes. One should familiarize himself/herself with the census questionnaires to make sure that the data one is comparing are collected in a similar manner. The Census Bureau often changes the collection categories or universe surveyed, thus resulting in changes in the data reported. Numerical changes over time (i.e., increase in persons of Hispanic origin; changes in ancestry counts, etc.) may be due to a change in procedures (question placement or wording), rather than a true demographic change. The ancestry question provides a case in point. Always asked on a sample basis, the question asks respondents to write in their ancestry or ethnic origin on a blank line. While the census includes an information booklet to assist respondents understand the intent of the questions, there is additional assistance in this question with examples of possible answers provided below the line. In 1990 the Census Bureau included Cajun as one of these examples. 1990 results showed a ten-fold increase in the country’s Cajun population. As there was no adequate demographic reason for this increase, the next best explanation was that the example provided led to a response bias as respondents, unsure of how to answer, found this to be an acceptable alternative.
In order to assist you in understanding the potential biases created by the 2000 Census, we have created this section as a way of highlighting the most important changes to the census between 1990 and 2000.
Perhaps the most important change in 2000 was the manner in which race data were collected and reported. Prior to the 2000 Census, respondents were asked to identify the race that they considered themselves to be (view question). They were instructed to indicate only ONE racial category, and, if they chose to report more than one, only the first category (according to the sequence of the questionnaire) was counted. In 2000, however, the census questionnaire allowed persons to indicate ONE OR MORE racial categories (view question). Persons were allowed to select from 6 racial categories. The six individual race categories, combined with the potential multi-race responses, produced a total of 63 mutually exclusive racial categories for tabulation. Since the 1990 Census did not allow for the reporting of multiple races, a direct one-to-one comparison of 1990 and 2000 is not possible. However, as less than 2% of the nation’s population identified themselves as belonging to two or more races, a comparison of 2000 single race categories with 1990 race categories can be made, with the understanding that there is a margin of error. For person requiring a higher degree of accuracy when comparing racial categories, researchers have developed several bridging techniques that slightly improve the accuracy of the comparison. More information on bridging techniques can be found at http://www.whitehouse.gov/omb/bulletins/b00-02.html.
Another major change to the way in which race was enumerated in 2000 was the separation of the Asian/Pacific Islander category. In the 1990 Census, Asians and Pacific Islanders were included in the same race category. In 2000, Asians were separated into one category and Native Hawaiians were included with Pacific Islanders to create a second category. Comparison of data between 1990 and 2000 can be easily done by adding the two 2000 categories together to equal the 1990 category. Detailed 1990 tabulations will also allow for the separation of Pacific Islanders so that the 2000 categories can be compared.
A final difference between 1990 and 2000 concerns the way in which people were asked to identify themselves as American Indian or Alaska Native. The 2000 Census asked persons to write in their tribe affiliation if either American Indian or Alaska Native. In 1990, only those choosing American Indian could write in their tribe, while Native Alaskans were only able to choose between Eskimo and Aleut.
In 1990, the question regarding marital status was asked on the short form (100% count) whereas it was asked on the long form (Sample count) on the 2000 Census form. Even though the 1990 data are more accurate than the 2000 data, direct comparisons can be made between censuses.
There were significant changes in how persons with disabilities were enumerated in the 2000 Census. The number of disabilities that persons were able to choose from were expanded, and the age of persons from whom which data were collected was expanded. In 1990, only persons over the age of 15 were enumerated, while the 2000 census included all persons over the age of 5. Direct comparisons between 1990 and 2000 disability data are not possible, though comparisons of detailed subsets by age and specific disability can be made.
The growing importance, and incidence, of grandparents acting as primary caregivers for children resulted in two questions being added to the 2000 Census. This was the first time that this question was asked (outside of national surveys) and thus comparisons with previous years are not possible.
Trend analysis, between 1990 and 2000, on unmarried partners is problematic, due to differences in coding between the two censuses. While the data for both years came from the 100% household relationship question, supporting data (such as marital status) had been moved to the sample form in 2000. This, coupled with research outside the Census Bureau, resulted in changes to the editing process of persons who indicated that they have a spouse who is of the same sex. Same-sex spouse responses were flagged as invalid to comply with the 1996 Federal Defense of Marriage Act (H.R. 3396) passed by the 104th Congress. This act instructs all federal agencies only to recognize opposite-sex marriages for the purposes of enacting any agency programs. In order for Census Bureau data to be consistent with this act and the data requirements of other federal agencies, same-sex spouse responses were invalidated.
As a result of changes in the processing routine, estimates of same-sex unmarried partners are not comparable between the 1990 and 2000 Census. The Census Bureau believes 2000 estimates of this category are better estimates than those produced in 1990. It should also be noted that estimates of opposite-sex unmarried partners, however, were not affected by these editing procedures and changes, and are comparable between the two censuses. In any case, comparisons of data between unmarried partners, both same-sex and opposite sex, must be done carefully. For further information on the editing process please see: http://www.census.gov/population/www/cen2000/samesex.html
Due to changes in the classification systems of industries and occupations (NAICS replacing SIC system for industry; revisions to the standard Occupational Classification (SOC) System for occupations), most comparisons between 1990 and 2000 are not possible. One must pay very careful attention to the changes to know how closely any specific industry or occupation in 2000 tracks with 1990. A good source of information on these changes can be found at: www.census.gov/hhes/www/ioindex.html
It is important to note that income figures for the 1990 Census cover calendar year 1989, and the 2000 Census uses calendar year 1999. To adjust 1989 dollars to 1999 dollars, multiply by 1.304650. This adjustment rate is based upon the Bureau of Labor Statistics’ Consumer Price Index.
The Census Bureau used two surveys to conduct the 2000 Census. The first survey, which is known as the “short form,” was sent to 83% of households in the United States. It consisted of 7 questions covering age, gender, race, and ethnicity (Hispanic origin), household relationship (used to categorize households by type), and housing tenure (owner v. renter). These same 7 questions also lead off the “long form,” or sample questionnaire, and thus cover all persons and households in the United States. Much of the data collected through the short form are required by the Constitution for the purpose of reapportionment and political redistricting. Click here to view the short form (Acrobat Reader required).
The other questionnaire, known as the “long form,” was sent to approximately 17% of all households in the United States. The long form contained the original 7 questions asked on the short form plus 26 additional population questions and 20 additional housing questions. These questions go into more detail about demographics, education, income, employment and housing characteristics. Because only 1 in 6 households receive the long form, the data collected are regarded as sample data because only a sample of the US population completes the form. While not required for redistricting purposes, there are a host of other federal programs that rely on the sample data to determine funding levels and program eligibility. Click here to view the long form (Acrobat Reader required).
The Census Bureau releases the vast majority of its census results in the form of summary data. These represent responses aggregated across people, or households, living in a specific geographic area – be it state, county, city or census block. In other words, summary data will provide you with the number of households in a particular city that have 3 or more vehicles, or the number of persons, 25 years or over, in your county with a bachelor’s degree. The structure and content of the summary data tables are predetermined and cannot be altered. If the Census Bureau has not tabulated the data in a particular way (for instance, poverty rates for persons 25-34 years of age), there is nothing that can be done to change that.
Microdata, on the other hand, are the individual records that contain information collected about each person and housing unit. The Census Bureau uses these confidential microdata in order to produce the summary data that go into the various reports, summary files, and special tabulations. Public use microdata samples (PUMS) are extracts from the confidential microdata taken in a manner that avoids disclosure of information about households or individuals. These files allow the user to produce tabulations that were not available in the summary tables. There is a limitation, however, in that the geographic areas for which PUMS data are available must have a minimum population of 100,000, so as to ensure confidentiality.
The information gleaned from the 2000 Census short and long forms are released in a series of Census Bureau data products over a 3 to 4 year period. The method of release is to first produce products from the 100% questions, and then to follow with products containing the sample items. The following is a partial list of these products, containing brief descriptions and release dates for Michigan.
  1. 100% Data Products

  2. Redistricting (Public Law 94-171) Summary File
    The first Census 2000 file to be released, it contains information needed for local political redistricting. Included in this file is racial/ethnic information for the total population and the voting age population (18 years of age and over). The lowest level of geography covered in this file is the census block (See Census Geography for a description of Census geographic terms).
    Demographic Profiles (100% only)
    New to the 2000 Census are demographic profiles, comprised of four tables. The first release, which contained only 100% data, was a single table with select housing and population characteristics. Later the Bureau released 3 additional tables based on the sample data. The lowest level of geography covered by Demographic profiles is the census tract.
    Summary File 1 (SF 1)
    Summary File 1 contains cross-tabulations of information collected from all population and housing 100% questions. This file contains information on age, gender, race, ethnicity, household relationship and housing characteristics. Summary File 1 contains a total of 286 tables. It important to note that while the lowest level of geography covered is the census block, certain population and housing tables (labeled PCT and HCT) only go as low as the census tract.
    Summary File 2 (SF 2)
    While Summary File 2 contains much of the same information as Summary File 1, its value is that many of its tables are iterated for a selected list of race and ethnic categories. There are 36 population tables (PCT) and 11 housing tables (HCT) for each of the 250 population groups. This results in a total of 11,750 tables. The 250 population groups cover the total population, 132 racial groups, 78 American Indian & Alaska Native categories and 39 Hispanic/Latino groups. The lowest level of geography covered by Summary File 2 is the census tract and all population groups are subject to a population threshold of 100 or more persons. This means that data are not reported for geographies where the population of a particular group is less than 100 persons.
  3. Sample Data Products

  4. Demographic Profile (Sample Data Only)
    This file contains the three tables discussed above. While Table 1 provides the 100% data items, Table 2 includes select social characteristics, Table 3 includes select economic characteristics, and Table 4 provides select housing characteristics. The lowest level of geography covered is the census tract.
    Summary File 3 (SF 3)
    Summary file 3 contains select cross-tabulations on ancestry, education, employment, occupation, income, poverty and housing characteristics. There are 31 population tables and 20 housing tables across 9 population groups (While alone, Black alone, American Indian & Alaska Native alone, Asian alone, Native Hawaiian & Other Pacific Islander alone, Other Race alone, Two or More Races, Hispanic/Latino, and White non-Hispanic alone). There is a total of 813 tables – 484 covering population and 329 covering housing. It important to note that while the lowest level of geography covered is the census block, certain population and housing tables (labeled PCT and HCT) only go as low as the census tract.
    Summary File 4 (SF 4)
    While Summary File 4 contains much of the information provided in Summary File 3, its importance derives from its tabulations by detailed race, ancestry and Native American tribes. The data are presented in 213 population tables and 110 housing tables for 336 population groups. These groups include the total population, 132 race groups, 78 American Indian & Alaska Native categories, 39 Hispanic/Latino groups and 86 ancestry groups. The lowest level of geography covered by Summary File 4 is the census tract and all population groups are subject to a population threshold of 50 or more persons in sample. This means that data are not reported for geographies where the population of a particular group enumerated in the sample is less than 50 persons.
  5. Other Data Products

  6. Public Use Microdata Samples:
    National Characteristics 1 Percent PUMS File
    The national characteristics file provides the maximum amount of social, economic, and housing information available. The goal of this file is to provide as close as possible the amount of detail that was in the 1990 PUMS files (and, in some cases, more detail). To maintain this level of detail, however, the minimum geographic population threshold must be raised above 100,000 (the PUMA minimum). A new geographical entity has been created--the super-PUMA. Super-PUMAs have a minimum population of 400,000 and are composed of a PUMA or PUMAs delineated on the companion state-level PUMA file. Each state is identified, and any state with a population of 800,000 or greater can be subdivided into two or more super-PUMAs.
    State-Level 5 Percent PUMS Files
    State-level 5 percent PUMS files provide information for PUMAs that will represent many metropolitan areas, cities, and more populous counties, as well as groups of less populous counties. In order to protect confidentiality, characteristic information for these smaller areas will be less detailed than in the national 1 percent file. Each geographic unit in the 5 percent files--PUMAs--must meet a minimum population threshold of 100,000. The minimum PUMA threshold will be held at 100,000 people by increasing the degree of variable collapsing to an appropriate level to maintain confidentiality. There are two main arguments favoring this approach. First, from a user's standpoint, raising the minimum population threshold for PUMAs above 100,000 would greatly restrict a wide variety of local-level geographic analyses, such as studies of nonmetropolitan, metropolitan, and intrametropolitan areas, conducted by public agencies, academic researchers, and others in the private sector. Second, the 100,000 minimum population threshold-- the threshold set for both the 1980 and 1990 PUMS files--permits historical comparability. Users interested in time-series analysis were clearly displeased at the possibility of an increase in the threshold for Census 2000.
For more information on the above listed data products and others, please see http://www.census.gov/population/www/censusdata/c2kproducts.html. For information on how to obtain the above listed data, please see the section: How to Obtain Data.
The following is a list of widely used data categories from the 2000 Census. Included in the description is their definition, how to use and interpret the information and how to calculate percentages (if applicable).
Total Population
Total population is the most straightforward and widely used statistic from the Census. This statistic is based upon 100% count data and is available from the block level to a national total. Because it is available at all levels of geography, it is one of the basic building blocks of the census and serves as the denominator for most population-based percentage calculations. A similar statistic, found in Summary Files 3 and 4, is Sample Population. Due to the fact that data in SF3 and SF4 files are derived from a sample of the population, the Census Bureau provides this count for use as a denominator when computing percentages for sample data.
Total Households
Like total population, the count of total households is one of the most basic data categories in the Census. In fact, census data collection is based upon households because questionnaires are mailed out to addresses (housing units) not persons. The householder completes the questionnaire for all persons in the house. There are two types of households - family and non-family. The question on household relationship is a 100% question and is found on the long and short form questionnaire. It is only answered when there is more than one person in the household, and then it is answered with regard to the person’s relationship to the householder. If there is only one person in the household, the census tabulates it as a 1-person, nonfamily, household. If there is more than one person, the household structure is determined by the responses given by persons 2, 3, etc.
Total Families (Family Households)
Family households consist of a householder and one or more other persons living in the same household who are related to the householder by birth, marriage or adoption. All persons in a household who are related to the householder are regarded as members of his or her family. A household can contain only one family for census purposes. The number of family households always equals the number of families; however, a family household may also include non-relatives living with the family. Families are classified by type as either a “married-couple family” or “other family,” which is further classified into “male householder” (a family with a male householder and no wife present) or “female householder” (a family with a female householder and no husband present).
Race/Hispanic Origin
One of the most common misconceptions about the Census is that Hispanic is considered a racial category. This is not true, as the Federal Government, and therefore the Census Bureau, considers Hispanic origin to be an ethnic designation. As a result, respondents are asked to provide a race in one question and asked in a separate question whether they are of Hispanic origin or descent. All counts of Hispanics contain a footnote that states, “Hispanics may be of any race.”
The concept of race, as used by the Census Bureau, reflects self-identification; it does not denote any clear-cut scientific definition of biological stock. The data for race represent self-classification by people according to the race with which they most closely identify. Furthermore, it is recognized that the categories of the race item include both racial and national origin or socio-cultural groups. The Census Bureau recognizes that there are persons who do not identify with a specific racial group, and thus the 2000-race question included an “Other Race” category with provisions for a write-in entry. For data product purposes, “Some other race” includes race responses not included in the “White,” “Black or African American,” “American Indian and Alaska Native,” “Asian,” or “Native Hawaiian and Other Pacific Islander” race categories. Respondents providing write-in entries such as multiracial, mixed, interracial, or a Hispanic/Latino group (for example, Mexican, Puerto Rican, or Cuban) are included in the “Some other race” category.
Persons of Hispanic origin are those who classified themselves in one of the Hispanic origin categories listed on the questionnaire - “Mexican,” “Puerto Rican,” or “Cuban” - as well as those who indicated that they were of “other Spanish/Hispanic” origin. Persons of Hispanic origin may be of any race. [According to the 2000 results, 12.5% (35,305,818) of the nation’s population identified as Hispanic origin. Of those, 47% (16,907,852) identified as being white and 48% (14,891,303) as some other race. The majority of their “other race” write-in responses were an Hispanic, Latino or Spanish population or country.]
The Census Bureau defines ancestry as a person’s ethnic origin or descent, roots, heritage, place of birth, or ancestors’ place of birth. The goal of the ancestry question is to measure the respondent’s identification with his/her ethnicity - be it single or multiple. Like race and Hispanic origin, ancestry is based upon self-identification of the respondent, but unlike them it is collected on a sample, not 100%, basis. Persons are allowed to report as many ancestries as they wish, but only the first two are tabulated. Basic ancestry data are reported in Summary File 3 (SF3) for the 2000 Census, and are tabulated in three ways – each of which provides counts of 110 ancestry categories. The first contains a count of first ancestry responses – comprised of persons indicating only one ancestry plus the first category of multiple-ancestry responses. The second tabulation only looks at the second response of multiple-ancestry responses – thus being additive to tabulation 1. The third table is a tabulation of all ancestries reported – a combination of the previous two. In order to calculate population share by ancestry, one needs to use total number of ancestries reported, rather than total population, as the denominator.
The age classification is based on the age of the person in completed years as of April 1, 2000. In the 2000 Census, respondents were asked for their age and date of birth, including month, day and year of birth (only years was asked in the 1990 Census). In the most detailed tabulation, age data are made available by single year to 100, and three categories above that. Data on age are used to determine the applicability of other questions for a person and to classify other characteristics in census tabulations. Age data are needed to interpret most social and economic characteristics used to plan and examine many programs and policies.
Poverty Status
Following the Office of Management and Budget's (OMB) Statistical Policy Directive 14, the U.S. Census Bureau uses a set of money income thresholds that vary by family size and composition to determine who is poor. The poverty measure is based on a definition originated by the Social Security Administration in 1964, modified by Federal interagency committees in 1969 and 1980, and prescribed by the Office of Management and Budget. The income levels used by the Census Bureau to determine the poverty status of families and unrelated individuals included a set of 48 thresholds, arranged in a two-dimensional matrix and consisting of family size cross-classified by presence and number of family members under 18 years old. Poverty status was determined for all persons except institutionalized persons, persons in military group quarters or in college dormitories, and unrelated individuals under 15 years old. These groups were excluded from the numerator when calculating poverty rates. The average poverty threshold for a family of four persons was $17,029 in 1999. If a family's total income is less than that family's threshold, then that family, and every individual in it, is considered to be "in poverty". The poverty thresholds do not vary geographically, but they are updated annually for inflation using the Consumer Price Index (CPI-U). The official poverty definition counts money income before taxes and does not include capital gains and noncash benefits (such as public housing, Medicaid, and food stamps).
Information on money income received in the calendar year 1999 was requested from persons 15 years and over. “Total income” is the sum of the amounts reported separately for the potential sources of income - 1) wage or salary income; 2) net nonfarm self-employment income; 3) net farm self-employment income; 4) interest, dividend, net rental or royalty income; 5) Social Security or railroad retirement income; 6) public assistance or welfare income; 7) retirement or disability income; 8) and all other income. “Earnings” is defined as the sum of wage or salary income, plus net income from farm and nonfarm self-employment. Receipts from the following sources are not included as income: money received from the sale of property (unless the recipient was engaged in the business of selling such property); the value of income “in kind” from food stamps, public housing subsidies, medical care, employer contributions for pensions, etc.; withdrawal of bank deposits; money borrowed; tax refunds; exchange of money between relatives in the same household; gifts and lump-sum inheritances, insurance payments, and other types of lump-sum receipts. (For more information, see “Public Assistance Income,” “Retirement Income” and “Social Security Income.”)
Educational Attainment
Educational Attainment refers to the highest level of school completed or the highest degree received. The category, “Associate degree” includes persons whose highest degree is an associate degree either in (1) an occupational program that prepares them for a specific occupation in which the course work may or may not be creditable toward a bachelor’s degree, or (2) an academic program, primarily in the arts and sciences, in which the course work is transferable to a bachelor’s degree. Examples of professional degrees include medicine, dentistry, chiropractic, optometry, osteopathic medicine, pharmacy, podiatry, veterinary medicine, law, and theology, but specifically exclude barber school, cosmetology, or other training for a specific trade.
Occupation describes the kind of work the person does on the job. For employed people, the data refer to the person's job during the reference week. For those who worked at two or more jobs, the data refer to the job at which the person worked the greatest number of hours. Some examples of occupational groups shown in this product include managerial occupations; business and financial specialists; scientists and technicians; entertainment; healthcare; food service; personal services; sales; office and administrative support; farming; maintenance and repair; and production workers. The Census utilizes the Standard Occupational Classification (SOC) system, which was most recently revised in 1998. The SOC is the federal government’s standard occupational classification system. It groups occupations according to the nature of the work performed, and relates these occupations to others of a similar nature. There are 23 major groups in the SOC and 821 detailed occupations within those groups.
As was the case with the change in the industrial classification system, the federal interagency SOC Revision Policy Committee (SOCRPC) decided similarly to rearrange the entire structure of the standard occupational classification rather than to start with the old SOC and simply try to make improvements. Unlike the NAICS, however, their end result was truly a major change. Analysis of occupational data across time will, as a consequence, be much more challenging.
Information on industry relates to the kind of business conducted by a person’s employing organization. For employed people the data refer to the person’s job during the reference week. For those who worked at two or more jobs, the data refer to the job at which the person worked the greatest number of hours. The 2000 Census utilized the new North American Industry Classification System (NAICS). NAICS codes replace the Standard Industrial Classification (SIC) codes used in previous censuses. NAICS classifies industries using 2-, 3-, 4-, 5-, and 6- digit levels of detail. 2-digit codes represent sectors, the broadest classifications. 6-digit codes represent individual industries in the U.S. Some examples of industrial groups shown in census products include agriculture, forestry, and fisheries; construction; manufacturing; wholesale or retail trade; transportation and communication; personal, professional and entertainment services; and public administration.
Census geography provides the framework for interpreting, analyzing, and understanding census data. The Census Bureau classifies all geographic entities into two broad categories:  1) legal and/or administrative entities, and 2) statistical entities. The geographic areas may work in a hierarchical fashion, with smaller areas nesting in larger ones (e.g., blocks in block groups; block groups in census tracts; census tracts in counties, etc.).  Some areas, like ZIP Code Tabulation Areas (ZCTAs), are not structured to nest (though at times they may nest within a city or county) and are thus given only as subsets of the nation (See Standard Hierarchy).
Legal/Administrative entities generally originate from charters, laws, treaties, resolutions or court decisions. They include:
Congressional District
One of the 435 areas from which people are elected to the U.S. House of Representatives.
The primary legal division of every state except Alaska and Louisiana. A number of geographic entities are not legally designated as a county, but are recognized by the Census Bureau as equivalent to a county for data presentation purposes. These include the boroughs, city and boroughs, municipality, and census areas in Alaska; parishes in Louisiana; and cities that are independent of any county in Maryland, Missouri, Nevada, and Virginia.
Incorporated Place
A type of governmental unit, incorporated under state law as a city, town (except in New England, New York, and Wisconsin), borough (except in Alaska and New York), or village, generally to provide a wide array of specific governmental services for a concentration of people within legally prescribed boundaries.
Minor Civil Division (MCD)
A type of governmental unit that is the primary governmental or administrative division of a county or statistically equivalent entity in many states and statistically equivalent entities. MCDs are identified by a variety of terms, such as township, town (in eight states), or district. The U.S. Census Bureau recognizes MCDs in 28 states, the District of Columbia, Puerto Rico, and the Island Areas. In 20 states and American Samoa, all or many MCDs are active general-purpose governmental units. Many MCDs are not general-purpose governmental units, and therefore do not have elected officials to carry out legal functions; instead, they serve as nonfunctioning administrative entities.
A primary governmental division of the United States. The Census Bureau treats the District of Columbia as the equivalent of a state for data presentation purposes. It also treats a number of entities that are not legal divisions of the United States (e.g. Island Areas) as the equivalent of states for data presentation purposes.
United States
The 50 states and the District of Columbia.
Statistical entities usually evolve from practice, custom, usage, or need, and generally the Census Bureau develops criteria and guidelines for their identification and delineation. They include:
Census Block
An area bounded on all sides by visible and/or non-visible features shown on a map prepared by the Census Bureau. A block is the smallest geographic entity for which the Census Bureau tabulates decennial census data. The census blocks were completely renumbered for Census 2000.
Block Group (BG)
A statistical subdivision of a census tract. A BG consists of all tabulation blocks whose numbers begin with the same digit in a census tract. BGs generally contain between 300 and 3,000 people, with an optimum size of 1,500 people. The BG is the lowest-level geographic entity for which the Census Bureau tabulates sample data from a decennial census.
A small, relatively permanent statistical subdivision of a county or statistically equivalent entity, delineated for data presentation purposes by a local group of census data users or the geographic staff of a regional census center in accordance with Census Bureau guidelines. Census tracts generally contain between 1,000 and 8,000 people. Census tract boundaries are delineated with the intention of being stable over many decades, so they generally follow relatively permanent visible features. However, they may follow governmental unit boundaries and other invisible features in some instances; the boundary of a state or county is always a census tract boundary. The 2000 Census marked the first time that the entire country was tracted, thus creating census tracts out of 1990"s tract equivalent of Block Numbering Areas (BNAs).
Metropolitan Area (MA)
A large population nucleus, together with adjacent communities that have a high degree of economic and social integration with that nucleus. (Some MAs are defined around two or more nuclei.) MA is a collective term, established by the federal Office of Management and Budget in 1990, to refer to metropolitan statistical areas (MSAs), consolidated metropolitan statistical areas (CMSAs), and primary metropolitan statistical areas (PMSAs).
Metropolitan Statistical Area (MSA)
An MSA is a metropolitan area (MA) that is not closely associated with another MA. An MSA consists of one or more counties, except in New England, where MSAs are defined in terms of county subdivisions (primarily cities and towns).
Primary Metropolitan Statistical Area (PMSA)
If an area that qualifies as a metropolitan area (MA) has a population of one million or more, two or more primary metropolitan statistical areas (PMSAs) may be defined within it if they meet official standards and local governments favor that designation. When PMSAs are established within a MA, the MA is designated a consolidated metropolitan statistical area.
Consolidated Metropolitan Statistical Area (CMSA)
An area becomes a CMSA if it qualifies as a metropolitan area, has a population of 1,000,000 or more, has component parts that qualify as primary metropolitan statistical areas (PMSAs) based on official standards, and local governments favor the designation. CMSAs consist of whole counties except in New England, where they consist of county subdivisions (primarily cities and towns).
Public Use Microdata Area (PUMA)
A geographic entity for which the US Census Bureau provides specially selected extracts of raw data from a small sample of long-form census records that are screened to protect confidentiality of census records. The extract files are referred to as public use microdata samples (PUMS). Public use microdata areas (PUMAs), which must have a minimum census population of 100,000 and cannot cross a state line, receive a 5-percent sample of the long-form records; these records are presented in state files. These Pumas are aggregated into super-Pumas, which must have a minimum census population of 400,000 and receive a 1-percent sample in a national file. Pumas and super-Pumas are mutually exclusive, that is, they use different records to create each sample. Data users can use these files to create their own statistical tabulations and data summaries.
All territory, population, and housing units located outside of urbanized areas and urban clusters.
All territory, population, and housing units located within urbanized areas and urban clusters.
Urbanized Area (UA)
Densely settled area that has a census population of at least 50000. The geographic core of block groups or blocks must have a population density of at least 1,000 people per square mile, and adjacent block groups and blocks with at least 500 people per square mile.
Urban Cluster (UC)
Consists of a geographic core of block groups or blocks must have a population density of at least 1,000 people per square mile, and adjacent block groups and blocks with at least 500 people per square mile that together encompass a population of at least 2,500 people, but fewer than 50,000 people.
ZIP Code Tabulation Area (ZCTA)
A statistical entity developed by the Census Bureau to approximate the delivery area for a US Postal Service 5-digit or 3-digit ZIP Code in the US and Puerto Rico. A ZCTA is an aggregation of census blocks that have the same predominant ZIP Code associated with the mailing addresses in the Census Bureau’s Master Address File. Thus, the Postal Service's delivery areas have been adjusted to encompass whole census blocks so that the Census Bureau can tabulate census data for the ZCTAs. ZCTAs do not include all ZIP Codes used for mail delivery.
Data from the 2000 Census are released in three main formats: Internet, File Transfer Protocol (FTP) and CD/DVD.The Census Bureau is moving away from providing printed data tables in publication format as was done in previous censuses. Data users must now rely on digital formats for their data needs. The following covers the three formats and how to access them.
  1. Internet
  2. Internet access to the data is through American FactFinder (http://factfinder.census.gov/servlet/BasicFactsServlet) and the Census 2000 Gateway (http://www.census.gov/main/www/cen2000.html). Once on these sites, users will be able to access a wide range of tables by either selecting data categories or geography.
  3. File Transfer Protocol (FTP)
  4. While American FactFinder will allow users to download data tables in several formats, advanced users may opt to download ASCII files for each state via http://ftp2.census.gov/
  5. CD/DVD
  6. In addition to the FTP site and American FactFinder, the Summary Files are available on CD-ROM (state by state) or DVD (all 50 states). Data are generally available in ASCII format. The Census Bureau has also release datasets with software that facilitates retrieval and manipulation of the data. Whether downloading information for a single area like a census tract, or a city or for a group of geographic areas (e.g., all counties, places, or ZIP Code tabulation areas in the country), the software simplifies the process and leads you through the steps.
There are a number of other helpful resources available to guide you through the Census maze. Among the best that we have found are the following:
Introduction to 2000 Census Data Products (US Census Bureau)
Census Guide 2000 (University of Michigan)
Census 2000 at ICPSR (Inter-University Consortium for Political and Social Research)
US Census Resources on the Web (University of Wisconsin-Madison)
Census Tutorial (Alaska Library Association)