An error was found in the published margins of error (MOE) for a small number of zero count estimates. This error impacted the zero count estimates for 7,006 geographic areas out of the 776,479 in 2010-2014 production (less than 1.0% of the geographies). Of the areas with this issue, 2,565 (36.6%) have published MOEs for their zero count estimates that were larger than they should have been. The other 63.4% of the areas have published MOEs which are too small. Most of these differences are minimal, usually between 2 and 5. For example, the published zero estimates and MOEs may be 0 +/- 11 instead of the correct value of 0 +/- 16 for some small affected areas.

Unlike the variance methodology used for most ACS estimates, a modeled approach is used to calculate MOEs for zero count estimates. Each geographic area is assigned specific model parameters that vary by state and by size categories. For the 2010-2014 ACS 5-year products, a small percentage of geographic areas were assigned the wrong size category, which caused the modeled MOEs to be incorrect for their zero count estimates.

Estimates which are not zero are unaffected. Additional procedures have been implemented to avoid this error from occurring in the future.

For more information about how the MOEs of zero count estimates are calculated, please view Chapter 12 Variance Estimation of the ACS Design and Methodology document.