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Some or all the variables of a particular table may be suppressed at the geographic area selected due to population thresholds. Some tables have geographic restrictions.
Even if a geographic area meets the population threshold, highly detailed tables might contain too many estimates with relatively high variance. Since 2005, data release rules based on the statistical reliability of the estimates have been used to identify tables where a large proportion of estimates have relatively low reliability. When identified, these tables are not released for a particular geographic area.
The main data release rule for the ACS tables works as follows: Every Detailed Table consists of a series of estimates and each estimate is subject to sampling variability that can be summarized by its standard error. If more than half of the estimates in the table are not statistically different from 0 (at a 90 percent confidence level), than the table fails the test and is restricted from publication. Learn more about data quality on the Data Suppression page.
Sometimes when a table does not meet these reliability tests, a simpler table that collapses some of the detailed lines together, called a "Collapsed Table," may be available for the original Detailed Table. The data release rules are applied to the Collapsed Table as well. If the Collapsed Table meets the requirement, then it is released. If it does not meet the requirement, none of the estimates for that particular table are released for the geographic area in question. Collapsed Tables are available for many, but not all, Detailed Tables. These release rules apply to 1-year period estimates. No data release requirements are applied to the 5-year period estimates