American Community Survey (ACS)

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Notice About Using the 1999 American Community Survey Estimates

Special Limitations of the 1999 American Community Survey Estimates

Significant Changes from 1998 to 1999

Notice About Using the 1999 American Community Survey Estimates

The 1999 American Community Survey estimates have some limitations, which they will not have in future years and therefore should be considered experimental.

1. First, these estimates do not reflect certain kinds of change in the racial and Hispanic origin distributions of the population in selected counties.
2. Second, there are potential problems caused by differences between the race and Hispanic origin questions on the American Community Survey questionnaire and the wording of these questions on the 1990 census.

In 2002, we will reissue the 1999 tables using weights based on Census 2000. We expect at that time that the tables for all the sites will provide accurate profiles.

In all counties but Bronx County, NY, we think the American Community Survey experimental estimates are generally representative of the characteristics of the counties. We will be able to confirm this conclusion when Census 2000 information is available in 2001.

However, in Bronx County, NY, the differences between the 1990 and 2000 questions, and the procedures that depend on the 1990 census, combine to distort the American Community Survey estimates. In particular, the statistical methods we used appear to overstate the number of people who identified as Black Hispanics, understate the number of people identified as Black non-Hispanics or White Hispanics, and greatly understate the number of people identified as White non-Hispanics. Because the characteristics of these groups differ, inaccuracies in the weights mean that the characteristics of combinations of these groups are also inaccurate.

The experimental estimates for Bronx County, NY remain on the American Community Survey website and the American Fact Finder so that data users can study them, but they should be used with great caution, since they do not necessarily provide an accurate profile of Bronx County. The estimates will be recalculated after Census 2000 data are available and revised weights for 1999 can be produced.

For the full text of this explanation, see Special Limitations of the 1999 American Community Survey Estimates.

Accuracy of the Estimates

To take best advantage of these new data we suggest that you become familiar with the underlying methodology. For example, in 1999 the American Community Survey used a different method to develop the standard errors - represented by the upper and lower bound columns found on each table. Thus, a person comparing 1999 and 1998 data might find that the standard error has gone up, down, or - in most cases - remained about the same. Any differences in the upper or lower bounds are likely to be a result of the changed standard error methodology and not a problem with the estimate. These methodological changes must be kept in mind along with standard statistical cautions that estimates from surveys are not based on complete counts of the population and are therefore, by their nature, subject to some variability.

Preliminary Estimates

The 1999 American Community Survey is part of the Census comparison phase of this project. Therefore, the Census Bureau is striving to make the American Community Survey data products as similar as possible to the corresponding Census 2000 data products.

Detailed tables for 1999 American Community Survey sites are posted on American FactFinder. These tables are as similar as possible to the Census 2000 sample tables. The 1999 American Community Survey detailed tables are a preview of the Census 2000 tables.

Data users should be aware of the following cautions:

• The 1999 American Community Survey tables are based on a smaller sample size than the Census 2000 sample tables.
• The 1999 American Community Survey tables are a subset of Census 2000 tables.
• Revisions in Census 2000 tabulation specifications may necessitate corresponding changes in the 1999 American Community Survey tables. If so, revised American Community Survey tables will be posted on American FactFinder.

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