the Census Bureau decided to make the margins of error much more “in your face” in ACS products; they are included in every table. He wondered whether margins of error were an issue in working with the 2000 data or whether error has become an issue for media users simply because they are so much more prominent in the ACS products. Fessenden answered that he thought that the different style of presentation in the ACS products is a big part of the concern; he reiterated that he and his colleagues have to be mindful of the margins of error in deciding what to print and how to format finished products. Patricia Becker (APB Associates) added, and clarified, that there were margins of error for long-form-sample estimates—that the number of cases for geographic areas were “buried in the back” of the products so that the standard errors could be calculated, with a lot of digging. She commented that “there were errors in the long-form data, particularly for small population groups or small geographic areas, and they are every bit as bad as [for] the areas in the ACS. Most reporters didn’t know about them; demographers did.” She suggested for the record that the margins of error on the long-form estimates in Campbell’s analysis might be much more favorable to the ACS.
Campbell Gibson (U.S. Census Bureau, retired) commented that it is good that the ACS makes the margins of error prominent in its products, but suggested that two points were missing from the discussion about comparing the ACS to past decennial censuses. One is that—as he understood it—the original sample size for the ACS was supposed to be about 3 percent of households per year, in which case a 5-year collection would more closely approximate the census long-form sample. But, for budgetary reasons, the ACS sample is about half that level. The other point (and, partially, a modest defense for suppressing the standard errors on the long-form products) is that the long-form samples yielded estimates only once every 10 years—a time span so long that changes in variables like percentage of foreign-born in an area could have changed so markedly that the question of whether the difference was significant from census to census was “kind of passé.” But the annual availability of estimates from the ACS naturally creates the temptation to compare data from one year to the next and—particularly for small areas—changes in some variables might be much more subtle.
Andrew Beveridge (Social Explorer, Inc; see Section 7–C) said that he wanted to add to this discussion his view on the ACS products’ presentation of margins of error in cases where there are very small numbers or proportions for a particular group or area. In those instances, the Census Bureau’s approach has been to publish margins of error that allow for negative counts or proportions. He suggested that the general ACS data products might be improved if the Bureau implemented the methodology it used in generating a special tabulation of languages spoken in households to determine requirements for alternate-language voting materials under the Voting Rights Act (see Chapter 7). In that work, the Bureau produced Bayesian estimates that directly borrow strength