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 incomesNot 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 IncomesNot 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 IncomeNot 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

 

 

Wave 3

 

Owner Occupied vs. Specified Owner Occupied – This is an important one. Tabulations of value, owner costs, mortgage status, and costs as a percentage of income in the Census use “Specified Owner Occupied” units as a base. The ACS is a better more inclusive universe and uses ALL owner occupied units. This means that changes between 2000 and 2005 data for any table that previously used specified units are NOT comparable.

 

Units in Structure - Comparable

 

Year Structure Built – Comparable

 

Rooms/Bedrooms – Comparable but could be impacted by ACS picking up seasonality.

 

Occupants per Room - Comparable concept though likely impacted by different residency rules.

 

Year Moved In – Comparable though may be impacted by different residency rules.

 

Vehicles Available – Comparable concept though likely impacted by different residency rules.

 

House Heating Fuel – Comparable though likely impacted by different residency rules and ACS picking up seasonality.

 

Kitchen Facilities – Comparable concept though may be impacted by residency rules and ACS picking up seasonality.

 

Plumbing Facilities – Comparable concept though may be impacted by residency rules and ACS picking up seasonality.

 

Value - Not comparable because of change in universe from specified units to all units. Comparable concept though may also be impacted by residency rules and ACS picking up seasonality.

 

Mortgage Status – Not comparable because of change in universe from specified units to all units. Also impacted by different residency rules and ACS picking up seasonality.

 

Owner Costs – Not comparable because of change in universe from specified units to all units. Also data may be impacted by residency rules and ACS picking up seasonality.

 

Owner Costs as a Percentage of Household Income – Not comparable because of change in universe from specified units to all units and lack of comparability in income measures.

 

Contract and Gross Rent – Comparable concepts though may be impacted by different residency rules and ACS picking up seasonality.

 

Gross Rent as a Percentage of Household Income - Not comparable due to lack of comparability in income measures. Affected, to a lesser extent, by change in universe from specified to all units.

 

Telephone - Comparable concept though may be impacted by residency rules and ACS picking up seasonality.

 

Vacancy Status – Comparable concept though definitely impacted by residency rules and ACS picking up seasonality.