2005 American Community Survey: General Comparability Issues

Issue	Census 2000	ACS 2005
Universe	Most tables include ALL residents (there may be age, race, etc. restrictions) Some tables are limited to the household population If geography is correct, PUMS or Advanced Query System can be used to generate tables limited to the household population, but there are other issues to be noted.	Tables are limited to the HOUSEHOLD POPULATION ONLY (there may be additional restrictions such as age or race) This will have a greater impact on areas with large group quarters facilities.
Residence Rules	Usual place of residence – Self identification of where you live most of the year. College students are supposed to be counted at their college address. Does not capture seasonality or second home location.	Current Residence – Counted at the sampled address if lived there most of the time in the last TWO MONTHS. College students might be counted at parent’s house during the later summer months. This will have a greater impact on areas with large seasonal populations such as college and resort communities. Seasonal destination areas may have population counted that would have lived elsewhere in the April 1, Census.
Collection Procedures Non-Response Follow-up	Primarily personal visit by short-term, moderately trained employees, being paid a relatively low wage for the area. Emphasis on counting number of people at address.	Conducted by long-term, highly-trained employees, being paid reasonably well for the area. Telephone follow-up in second month if possible. Personal visit in third month usually to 1/3 of addresses not responding. Emphasis is on collecting characteristics of individuals in the household.
Proxy Respondents	Allowed - People living outside the address (landlords, neighbors, etc.) are allowed to provide information.	NOT Allowed - ONLY people living at the address can answer the questions.
Reliability	Statistical reliability is generally not reported, but can be calculated Generally, fairly small compared to the estimate. (Confidence intervals on data from PUMS will be larger.)	Reported as Margin of Error (MOE). Must be calculated for user derived data Can be VERY large compared to the estimate. MUST be used for comparing areas or change over time.

ITEM SPECIFIC COMPARABILITY

Total Population – Not Comparable – Unless otherwise noted, the 2000 Census reports the total resident population. The ACS reports only the household population. The ACS does NOT yet include group quarters.

Age – Concept is comparable but the Census reports age as of April 1, 2000. The ACS reports age as of the survey month.

Gender - Comparable

Race – Comparable

Hispanic or Latino Origin – Comparable

Household Relationship – Comparable though some categories are different. The Census distinguishes between Natural-born, Adopted, and Step sons and daughters while the ACS has only one category “Son or Daughter”. The Census also distinguishes between Parent-in-low and Son or Daughter-in-law while the ACS includes only the category “In-Law”.

Average Household/Family Size – Comparable though the different residency rules will likely impact household and family size.

School Enrollment – Concept is comparable but the reference period for Census is April 1, 2000 while the ACS reference period is the survey month. May also be affected by the ACS not including group quarters population.

Educational Attainment – Concept is comparable but the reference period for Census is April 1, 2000 while the ACS reference period is the survey month.

Marital Status – Concept is comparable but the reference period for Census is April 1, 2000 while the ACS reference period is the survey month. May also be affected by the ACS not including group quarters population.

Fertility – Not included in the 2000 Census

Grandparents – Comparable

Veterans Status – Comparable

Disability - Not comparable because the question was redesigned and because of the lack of non-institutional group quarters population in the 2005 ACS.

Residence 1 Year Ago – Not comparable because the Census question related to residence 5 years ago.

Place of Birth/Nativity – Comparable

Citizenship – Comparable

Year of Entry – Comparable

Region of Birth - Comparable

Income – Not Comparable – While the concepts are similar, there are several issues that make the data not comparable: differences in the time periods for which data are collected in the ACS versus the Census; adjustments for inflation in the ACS data; accuracy of the respondents’ answer; and the rates of imputation when the Census Bureau cannot get answers to these questions.

Reference Period – The 2005 ACS asks respondents for their income over the 12 months prior to completing the questionnaire. The 2000 Census asks respondents about their income in calendar year 1999.

Inflation Adjustment – Since the income data on the ACS is collected over an entire year, it refers to incomes received over a 23 month period (12 months prior to January 2005 through 12 months prior to December 2005). The Census Bureau adjusts incomes to represent the same time period using the Bureau of Labor Statistics’ Consumer Price Index for all urban consumers – research series (CPI-U-RS).

Accuracy of the Respondent’s Answer – Respondent accuracy can depend on the relative stability of the respondent’s income and their ability to recall changes, especially if there are major fluctuations in their income. The 2000 Census asks about income in 1999 at a time when most respondents have the information needed to complete their income taxes. It may be more difficult for an ACS respondent to recall income over the previous 12 months.

Imputation of Non-Response – Historically, rates of imputation for non-response in the ACS have been much lower than in the 2000 Census because of the use of highly training interviewers in the ACS. In the 2000 Census about 33 percent of all New York residents 15 and older had income imputed versus about 25 percent in the ACS.

Household and family incomes – Not comparable - Concepts are comparable but in addition to the issues above, they are also affected by differences in household composition due to the different residence rules used in the 2000 Census and the ACS

Per Capita and Aggregate Incomes – Not comparable - Concepts are comparable but the 2005 ACS excludes the incomes of people living in non-institutional group quarters (college dormitories, military barracks, etc.) and uses the household population as the base while the 2000 Census includes these incomes and uses the total population as the base.

Source of Income – Not comparable - Concepts are comparable in that definitions are consistent between the Census and the ACS, but the data are impacted by all of the general income qualifications.

Poverty Status – Not comparable - Since poverty status is based on income, it is subject to all of the problems described under income. Additionally, poverty status in the 2000 Census refers to poverty status during 1999. In the ACS poverty status refers to the 12 months prior to completing the questionnaire. The difference in residency rules can also affect the number of people in a family, changing the poverty threshold for that family, but might not have much of an effect on the family’s income.

Employment Status – Not Comparable - The concept is comparable in that both the 2000 Census and the ACS ask for employment status last week. However, in the Census the reference week is the last week in March whereas the ACS reflects an annual average collected throughout the year.

Means of Travel to Work – Generally comparable - In areas with large seasonal workforces or commuting methods affected by weather, such as walking, the data may not be comparable due to different reference periods. Also, “public transportation” included taxicabs in the 2000 Census but the 2005 ACS excluded this category.

Industry, Occupation, and Class of Worker - Generally comparable - In areas with large seasonal workforces the data may not be comparable due to different reference periods.

Weeks Worked – Comparable

Hours Worked – Comparable

Place of Work – Comparable

Time Leaving Home – Comparable

Travel Time to Work – Comparable

Source: NC State University Libraries