American Community Survey

The entire population continually ages into older age groups over time and babies fill in the youngest age group. So, the population of a certain age is made up of a completely different group of people in 2000 and 2007. Since populations occasionally experience booms/increases and busts/decreases in births, deaths, or migration (for example, the postwar Baby Boom from 1946-1964), one should not necessarily expect that the population in an age group in Census 2000 should be similar in size or proportion to the population in the same age group in different data year(s). For example, Baby Boomers were age 36 to 54 in Census 2000 while they were age 43 to 61 in the 2007 ACS 1-year and between ages 41 to 61 in the multiyear 2005-2007 period. So, the age group 55 to 59 would show a considerable increase in population when comparing Census 2000 data with the single year or multiyear ACS data.

Ancestry is the only item for which a "not reported" category is published since missing ancestries are never assigned or allocated. The extent of missing ancestry answers was higher in Census 2000 than in the ACS. The difference in the level of response may contribute to the difference in the two distributions.

Census 2000 represents data collected as of April 1, 2000 and thus the "2000" year of entry category accounts for the first quarter (Jan-Mar) in 2000 only. The ACS represents data collected throughout the entire year and thus the "2000" year of entry category accounts for the entire year of 2000

The ACS asked for residence 1 year ago whereas Census 2000 asked for residence 5 years ago.

The ACS excludes taxicabs in the tabulation category of "public transportation" and includes them in the category "taxicab, motocycle, bicycle or other means." However, Census 2000 includes taxicabs in the "public transportation" tabulation category.

The ACS used a joint relationship/marital status edit and Census 2000 did not. Also, Census 2000 provided more response categories than the ACS.

Census 2000 had more detailed relationship categories used to derive estimates of subfamilies than the ACS.

The ACS used a joint relationship/marital status edit and Census 2000 did not.

The question was not asked in Census 2000.

The ACS reference period was 3 months preceding the date of interview, while the Census 2000 reference period was any time since February 1, 2000.

The ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months." Census 2000, however, collected the income data for a fixed period of time -- "during 1999" (the last calendar year). For example, the 2007 ACS 1-year data reflect incomes over 2006-2007 and the 2005-2007 ACS 3-year data reflect incomes over 2004-2007. In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on the differences of income in the ACS and Census 2000, see Income in the American Community Survey:Comparison to Census 2000. For specific questions and answers about sources of poverty data, see Questions and Answers about Sources of Poverty Data [PDF 130K].

As ACS data are collected every month of the year, adjacent years will have some reference months in common. Hence, comparing the 2007 ACS with the 2006 ACS estimates is not an exact comparison of the economic conditions in 2007 with those in 2006. For a discussion of this and related issues, see Hogan, Howard, "Measuring Population Change Using the American Community Survey," Applied Demography in the 21st Century, Steven H. Murdock and David A. Swanson eds., Springer Netherlands, 2008. For specific questions and answers about sources of poverty data, see Questions and Answers about Sources of Poverty Data [PDF 130K].

The ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months." Census 2000, however, collected the income data for a fixed period of time -- "during 1999" (the last calendar year). For example, the 2007 ACS 1-year data reflect incomes over 2006-2007 and the 2005-2007 ACS 3-year data reflect incomes over 2004-2007. In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on the differences of income in the ACS and Census 2000, see Income in the American Community Survey:Comparison to Census 2000. For specific questions and answers about sources of poverty data, see Questions and Answers about Sources of Poverty Data [PDF 130K].

As ACS data are collected every month of the year, adjacent years will have some reference months in common. Hence, comparing the 2007 ACS with the 2006 ACS estimates is not an exact comparison of the economic conditions in 2007 with those in 2006. For a discussion of this and related issues, see Hogan, Howard, "Measuring Population Change Using the American Community Survey," Applied Demography in the 21st Century, Steven H. Murdock and David A. Swanson eds., Springer Netherlands, 2008. For specific questions and answers about sources of poverty data, see Questions and Answers about Sources of Poverty Data [PDF 130K].

The ACS disability questions are different from the Census 2000 disability questions, thus comparisons cannot be made.

The ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months." Census 2000, however, collected the income data for a fixed period of time -- "during 1999" (the last calendar year). For example, the 2007 ACS 1-year data reflect incomes over 2006-2007 and the 2005-2007 ACS 3-year data reflect incomes over 2004-2007. In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on the differences of income in the ACS and Census 2000, see Income in the American Community Survey:Comparison to Census 2000. The Census Bureau recommends using CPI-U-RS adjustment factors published annually by the Bureau of Labor Statistics (BLS) to adjust 1999 median, mean, and per capita income dollar amounts shown in Summary File 3 to 2007 dollars by multiplying the 1999 dollar amounts by the CPI-U-RS factor of 1.24438087. For CPI-U-RS inflation adjustment factors for other years see: BLS Consumer Price Index. Furthermore, direct comparisons of income and earnings distributions between Census 2000 and the 2007 ACS are not possible due to inflation. Users interested in making distribution comparisons need to inflation adjust individual income records using the Public Use Microdata Samples (PUMS) files from Census 2000

As ACS data are collected every month of the year, adjacent years will have some reference months in common. Hence, comparing the 2007 ACS with the 2006 ACS estimates is not an exact comparison of the economic conditions in 2007 with those in 2006. For a discussion of this and related issues, see Hogan, Howard, "Measuring Population Change Using the American Community Survey," Applied Demography in the 21st Century, Steven H. Murdock and David A. Swanson eds., Springer Netherlands, 2008.

The ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months." Census 2000, however, collected the income data for a fixed period of time -- "during 1999" (the last calendar year). In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on the differences of income in the ACS and Census 2000, see Income in the American Community Survey:Comparison to Census 2000. The Census Bureau recommends using CPI-U-RS adjustment factors published annually by the Bureau of Labor Statistics (BLS) to adjust 1999 median, mean, and per capita income dollar amounts shown in Summary File 3 to 2007 dollars by multiplying the 1999 dollar amounts by the CPI-U-RS factor of 1.24438087. For CPI-U-RS inflation adjustment factors for other years see: BLS Consumer Price Index. Furthermore, direct comparisons of income and earnings distributions between Census 2000 and the 2007 ACS are not possible due to inflation. Users interested in making distribution comparisons need to inflation adjust individual income records using the Public Use Microdata Samples (PUMS) from Census 2000.

As ACS data are collected every month of the year, adjacent years will have some reference months in common. Hence, comparing the 2007 ACS with the 2006 ACS estimates is not an exact comparison of the economic conditions in 2007 with those in 2006. For a discussion of this and related issues, see Hogan, Howard, "Measuring Population Change Using the American Community Survey," Applied Demography in the 21st Century, Steven H. Murdock and David A. Swanson eds., Springer Netherlands, 2008.

The ACS collects data throughout the year on an on-going, monthly basis and asks for a respondent's income over the "past 12 months." Census 2000, however, collected the income data for a fixed period of time -- "during 1999" (the last calendar year). For example, the 2007 ACS 1-year data reflect incomes over 2006-2007 and the 2005-2007 ACS 3-year data reflect incomes over 2004-2007. In a comparison study between Census 2000 income data and the 2000 ACS, income collected in Census 2000 was found to be about 4 percent higher than that in the 2000 ACS. For more information on the differences of income in the ACS and Census 2000, see Income in the American Community Survey:Comparison to Census 2000. The Census Bureau recommends using CPI-U-RS adjustment factors published annually by the Bureau of Labor Statistics (BLS) to adjust 1999 median, mean, and per capita income dollar amounts shown in Summary File 3 to 2007 dollars by multiplying the 1999 dollar amounts by the CPI-U-RS factor of 1.24438087. For CPI-U-RS inflation adjustment factors for other years see: BLS Consumer Price Index. Furthermore, direct comparisons of income and earnings distributions between Census 2000 and the 2007 ACS are not possible due to inflation. Users interested in making distribution comparisons need to inflation adjust individual income records using the Public Use Microdata Samples (PUMS) files from Census 2000.

As ACS data are collected every month of the year, adjacent years will have some reference months in common. Hence, comparing the 2007 ACS with the 2006 ACS estimates is not an exact comparison of the economic conditions in 2007 with those in 2006. For a discussion of this and related issues, see Hogan, Howard, "Measuring Population Change Using the American Community Survey," Applied Demography in the 21st Century, Steven H. Murdock and David A. Swanson eds., Springer Netherlands, 2008.

Since Census 2000, the period of military service categories on the ACS questionnaire were updated to: 1) include the most recent period "September 2001 or later;" 2) list all "peace time" periods without showing a date-breakup in the list; and 3) update the Korean War and World War II dates to match the official dates as listed in US Code, Title 38. While the response categories differ slightly from those in Census 2000, data from the two questions can still be compared to one another.

Due to an editing error, veteran's period of service (VPS) prior to 2007 was being incorrectly assigned for some individuals. The majority of the errors misclassified some people who reported only serving during the Vietnam Era as having served in the category "Gulf War and Vietnam Era." The remainder of the errors misclassified some people who reported only serving between the Vietnam Era and Gulf War as having served in the category "Gulf War."

The ACS has two separate questions, whereas in Census 2000, it was a two part question. However, the actual questions remain the same.

The question was not asked in Census 2000 thus comparions cannot be made.

The reference periods are different due to year-round ACS data collection. The ACS reference period is the week prior to the respondent completing the interview, or the field representative conducting the interview. Because questionnaires are mailed-out and field interviews are conducted throughout the year, there is a revolving reference period. For Census 2000, the reference period was the week prior to Census Day (April 1, 2000). The Census 2000 Summary File 3 (SF3) labor force data for some places where colleges are located appear to overstate the estimates of people in the labor force, the unemployed, and the percent unemployed because of data capture errors.

The ACS reference period is 12 months preceding the date of interview, while the Census 2000 reference period was the 1999 calendar year.

The ACS reference period is 12 months preceding the date of interview, while the Census 2000 reference period was the 1999 calendar year.

The Census 2000 tables use different tabulation categories than the ACS. However, PUMS data for Census 2000 and the ACS may be compared. When available, compare like universes.

The ACS codes are based on the 2002 North American Industry Classification System (NAICS) and are 4-digit codes, whereas Census 2000 codes are based on the 1997 NAICS and were 3-digit codes. Codes and descriptions, particularly within the Electronic Shopping, Internet Services, and Wholesale categories changed. Also, the Census 2000 tables did not include the "full-time, year-round" population and there were no median earnings Industry and Occupation tables. Thus, comparisons cannot be made for this population or characteristic.

For Census 2000, tables were not released for total renter-occupied units. The universe in the ACS is "renter-occupied housing units" whereas in Census 2000 the universe was "specified renter-occupied housing units," thus comparisons cannot be made.

For Census 2000, tables were not released for total renter-occupied units. The universe in the ACS is "renter-occupied housing units" whereas in Census 2000, the universe was "specified renter-occupied housing units," thus comparisons cannot be made.

With a mortgage/without a mortgage released in Census 2000 for both total owner-occupied units and specifed owner-occupied units.

For Census 2000, tables with full distribution were released for total owner-occupied units but medians were not shown. When available, compare like universes.

The universe in the ACS is "owner-occupied housing units" whereas in Census 2000, the universe was "specified owner-occupied housing units," thus comparisons cannot be made.

For Census 2000, tables with full distribution were released for total owner-occupied units but medians were not shown. When available, compare like universes.

The tabulation category "Rented or sold, not occupied" in Census 2000 is separated into two categories "Rented, not occupied" and "Sold, not occupied" in the ACS.

The ACS has allows a write-in for values over $250,000. For Census 2000, tables with full distribution, medians, and aggregate values were released for specified owner-occupied units as well as total owner-occupied units. When available, compare like universes.

The total group quarters (GQ) population in the ACS may not be comparable with Census 2000 because: 1) There are some Census 2000 GQ types that were out of scope in the 2007 ACS such as domestic violence shelters, soup kitchens, regularly scheduled mobile food vans, targeted non-sheltered outdoor locations, crews of maritime vessels and living quarters for victims of natural disasters. Also, there are some Census 2000 GQ type categories that are no longer valid (residential care facility providing "Protective Oversight," hospitals/wards for the chronically ill and hospitals/wards for drug/alcohol abuse). The exclusion of these GQ types from the ACS may result in a small bias in some ACS estimates to the extent that the excluded population is different from the included population. 2) A sample of GQ facilities throughout the United States and Puerto Rico were selected for the ACS. ACS controls the GQ sample at the state level only. Therefore, for lower levels of geography, particularly when there are relatively few GQs in a geographic area, the ACS estimate of the GQ population may vary from the estimate from Census 2000. The 2005-2007 data is the weighted combination of 2006 and 2007 data. Therefore, the 3-year data must also be compared with caution.

The weighting for the group quarters (GQ) population is controlled at the state level, but not at sub-state levels. For this reason, users may observe greater fluctuations in year-to-year ACS estimates of the GQ population at sub-state levels than at state levels. The causes of these fluctuations typically are the result of either GQs that have closed or where the current population of the GQ is significantly different than the expected population as reflected on the sampling frame. Substantial changes in the ACS GQ estimates can impact ACS estimates of total population characteristics for areas where either the GQ population is a substantial proportion of the total population or where the GQ population may have very different characteristics than the total population as a whole. Users can assess the impact that year-to-year changes in sub-state GQ total population estimates have on the changes in total ACS population estimates by accessing Table B26001 on American Fact Finder. Users should also use their local knowledge to help determine whether the year-to-year change in the ACS estimate represents a real change in the GQ population or may be the result of the lack of adequate population controls for sub-state areas.