What's NewIt's getting close again. We are less than a year away from the next Decennial Census day - April 1, 2010. Which means we are less than two years away from seeing the first tabulated results of that once-in-a-decade survey. Less than two years away from knowing with near certainty just how many people live in our counties, our cities and our neighborhoods, regardless of size. Not only will we know the head count but we'll also know important demographic details of the population: age, race, gender, hispanic origin, living in a household (and whether it's a family household) or in group quarters (what kind), renters or owners, etc. Or at least we'll know these things as they were circa that point in time - April 1, 2010. So we can easily spot trends by linking to comparable data gathered on April 1, 2000 and even April 1, 1990.
What else are we looking forward to getting from the new census? Won't we also be getting new data regarding things such as people's incomes, poverty status, education, occupation, employment status, house values, and disabilities? Well, no. Not from the decennial census, not this decade.
Because now that we have the ACS (the American Community Survey - see www.census.gov/acs/www/index.html for details) we won't be needing that portion of the decennial census where these kinds of data have been collected and reported for decades. The long and short of it is there will be no long form questionnaire used for the 2010 census, only the short form with its seven basic questions per person. Fewer questions being asked about fewer subjects results, of course, in fewer tables dealing with fewer subjects being published based on the survey.
But we do have data regarding these subjects based on the American Community Survey. The ACS was created so that we would have such data not just once every ten years, but once every year of the decade. We have been getting such data based on the ACS since 2006, based on surveys conducted nationwide starting in 2005. So does this mean we are not going to miss the long form (aka "sample") data from the decennial census? The answer is not so simple. It depends on what you are looking for. Perhaps the most critical factor is the size of the geographic areas for which you want to see data. If you are a person who focuses on the "big picture" - what is happening nationwide or statewide - or even city or countywide for larger cities and counties then you are probably going to be pretty happy with the ACS as a replacement for the Long Form. But if you need data for smaller areas, for your town of 10,000 people or your local wards, planning areas or transportation zones then you may not be as happy with what's new.
What's The Difference?Back in 2002 when the first long form-based/sample results were published based on the 2000 Census, users were able to get detailed socio-economic data such as median incomes and poverty rates for all kinds of geographic areas. You could get data for the nation, your state, your county, your town or township (county subdivision), your ZIP code, your neighborhood (census tract or block group), your city (regardless of size), etc. These data were delivered in a data product called Summary File 3. The data were published for every county, every city, every town or township, every ZIP code, every census tract and block group in the country. There was no suppression in the data. There were some real issues with sampling error for very small geographic areas, but for the most part no attempts were made by the Census Bureau or those intermediaries providing access to these data to call attention to potential problems due to such issues. (There are links to data notes when accessing SF3 tables in the AmericanFactfinder web application, but nothing that would allow you as a practical matter to readily evaluate the data with respect to margins of sampling error.)
We do not exactly have something comparable to Summary File 3 based on the ACS yet. One could argue that we never will. We do have a set of base (or "detailed") tables and a set of standard extract/profiles available via AFF (the Census Bureau's American FactFinder web site) that are similar to the kinds of data that can be extracted from SF3. But the similarities are (for now, at least) probably outweighed by what's different. The differences include:
How The ACS Is Better Than The Decennial Long Form
How The Decennial Census Long Form Is (Was) Better Than The ACS
The Bottom LineSo what is the answer to the question posed in the subtitle? Are we better off with the ACS instead of the Long Form? Based on what you've read on this page you might be inclined to say the answer is No. The ACS has got a lot of things that do not compare favorably with the old reliable Long Form. But just because we listed 6 things where it was inferior and only 3 where we judged it to be better, that does not necessarily mean the bottom line says it loses. You really have to assign weights to these comparison items to reflect their importance. The one item of those discussed that can outweigh all the others is the first one in the Why the ACS is Better section: 1. Timeliness for areas that are large enough to get new data every year. This aspect of the ACS is really why it was invented. The details about how it was going to be done, having to do with sample sizes, weighting schemes, data suppression rules, etc. were all minor details. Most of the negative things we have said about the ACS here really do not apply much when you are looking at data for the nation, for a state, a major city or metro area. Problems with sampling just don't make much difference at these levels. It will be very helpful to get ACS data for 2009 in the fall of 2010, so that we can study in great detail the effects of the economic recession across the country. You may not be able to study it down to the neighborhood, but that is not an appropriate level for the typical "big picture" analysis anyway.
And even at much smaller levels, there are those who would argue that these data really aren't all that much worse than the SF3 data, we are just more aware of it because of the emphasis being placed on MOE's and other measures of sampling error. I do not agree with that viewpoint, but I have heard it.
By far the most significant negative aspect of the ACS as a replacement for the long form is the lack of good data for smaller geographic areas. The 2000 decennial census allowed us to know (for example) that of the approximately 6,800 residents of Livingston, Montana about 12.1% had incomes that put them at or below the poverty level, and that 4.6% had incomes that were below 50% of that poverty threshold. Some time late in 2010 we should be getting some new figures of this sort for Livingston, but it's going to be much less convincing, assuming it is not suppressed. It will be based on data collected going back to January of 2005. It might well be that the poverty situation of 2005 through 2007 may have been somewhat different than that of 2008-2009; but such differences will all be smoothed over with period estimates. We'll eventually be able to adjust the focus to try and get a clearer picture of poverty in Livingston (or any of the other tens of thousands of American towns with populations below 20,000) as we get those annual "updates" that are only 1/5th new and 4/5 the same as last year.
We are going to have to make adjustments as we learn to accept and live with data that are spread out over five years. We understand the concept, and we understand that there are an awful lot of small rural counties, small towns out on the prairie, and even established neighborhoods in older cities and suburbs that change so slowly that taking a snapshot with a 5-year time exposure will not significantly blur the picture at all. Some places never change, or evolve so slowly that it takes years to notice anything. If you are interested in tracking change for small areas it is going to require having ten consecutive years of ACS data so that you can look at data for two adjacent and non-overlapping 5-year periods. That should be something we can do starting around 2015.
- Ten Things to Know to Know About the American Community Survey (Missouri Census Data Center)
- American FactFinder to access SF3 data (2000 census) and ACS data (various time periods).
- American Community Survey home page (at the Census Bureau).
- American Community Survey Readme file at the Missouri Census Data Center web site .