What happened to the Census?

The year 2010 marks the last for the decennial Census.  Although you might miss the ad campaigns every 10 years, the Census hasn’t really disappeared completely.  Instead, it’s being replaced by the American Community Survey (ACS).  Although the goals of the ACS are similar to those of the Census, its approach is very different.  Rather than survey all individuals each year, the ACS surveys about 250,000 addresses per month (i.e., 3 million addresses/year).  This amounts to a survey of about 2.5% of households each year.

The Missouri Census Data Center notes some of the pros and cons of the change.


  • The ACS provides a more current picture of the country.  Currently, the latest Census data is available for the year 2000 while in December the ACS will release figures for 2009.
  • New questions can be added to the survey without having to wait for the decade to change
  • Researchers can calculate statistics at the national, state, MSA, large city,  counties, and even PUMAs every year.


  • The sampling error associated with the decennial census long form data is much lower (in general) than that of the ACS.
  • Data for smaller geographic areas (especially those under 20,000 as well as for all ZIP codes, even those with populations over 20,000), are only released as 5-year period estimates.
  • Sampling methodology relies on the accuracy of Census population estimates.
  • Since using data for small area requires the use of a sample taken over a 5-year period, it will be impossible to use the ACS data to pinpoint areas that may be undergoing significant changes over the period.

Overall, the key benefit of the ACS is that it provides more timely responses while the drawback is that the pool of household sampled in a given year is much less than is the case for the decennial Census.

I have also made this spreadsheet to compare the ACS to the decennial Census.

1 Comment

  1. As I understand it, the decennial census is not really going away. The ACS is replacing what used to be called the “long form”, but the short form will still be delivered to every household in 2020.

    So no need to mourn the loss of those great ads. They’ll be back in 10 years or so.

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