What's the Difference Between the US Census and ACS?

Our Excel add-in CDXZipStream has data feeds from the American Community Survey (ACS) and decennial, 10-year census, both of which are sourced from the U.S. Census Bureau.  How do you pick which one to use?  Here are the major differences between the two that can help you decide:

1. Frequency: The decennial census is performed once every ten years, while the ACS is performed yearly.  

2. Sample Size: As specified by the Constitution, the decennial census must get a complete count of the population in order to allocate representation in the House, and so population estimates are not sufficient for this purpose. To obtain this count, the census of 2010 sent forms to about 117 million households. The American Community Survey, which helps direct how federal and state funds are distributed, obtains responses from about 3 million households each year, so all of its data are estimates.

3. Error: Since the decennial census is a total count, there is no calculated error associated with the resulting data. (Obviously there is some small error, but it is not reported.)  The ACS, as a survey, does provide measures of sampling error for its published estimates, either as 90 percent margins of error or confidence intervals.  These errors are not included as part of the CDXZipStream ACS data feed.  For more information about ACS error estimation, please see the document ACS Design Methodology

4. Sample period: The decennial census is designed to be a snapshot of the U.S. population every ten years, while the ACS provides a more continuous, moving portrait.  In order to provide statistically significant data for smaller geographies, the ACS data is also aggregated over 3 and 5 year periods; the CDXZipStream ACS data feed is aggregated over 5 years to provide data down to the census tract level.

5. Data:  Currently the decennial census gets basic data about population counts, age, race, ethnicity, gender, and household size.  The American Community Survey, which uses many of the same questions from the old “long form” of the census, is more broad in scope since it will be used for allocating governmental budgets.  It therefore also includes some of the more interesting demographic areas that are helpful for developing marketing strategies for business.

Decennial census data from 2010 are provided for ZCTA’s (the census version of ZIP Codes), in these areas:  age (by gender), total population (by gender), household size, mortgage status, ethnicity, and race.

ACS data feeds in CDXZipStream cover the following areas: age (by gender), total population (by gender), individual earnings (by gender), educational attainment (by gender), household size and income, housing value and mortgage status, marital status (by gender), ethnicity, race, rental data, and school enrollment (by gender).  These data are provided for census tracts, ZCTA’s city, county, state, and Core Based Statistical Area (CBSA).

For a complete listing of all data variables available through CDXZipStream, please download the document CDXZipStream Data Feeds and Definitions.

Here’s a short video showing how to use CDXZipStream to get income and earnings data from the ACS:

Add comment