The Census Bureau recently discovered several small errors in the ACS processing system. The erroneous code was identified and corrected in July, 2011, and data processed since then have been handled appropriately. This note briefly describes the errors and the impacted variables.

The code errors existed in the processing of paper questionnaires included in the ACS Failed Edit Follow-Up (FEFU) operation, causing a very small amount of self-reported data from the mail questionnaires to be omitted. The FEFU operation involves follow-up phone calls for paper forms that contain incomplete responses. In many instances, the original responses were re-captured in the follow-up interview.

The following items were affected by the errors, but had no notable impact on the published estimates at the national level: Minutes to work, Class of worker, Available to start work last week, Worked 50 or more weeks during the past 12 months, Relationship, Year moved in, and Year built. The errors appear to be spread throughout the United States, and we have no reason to believe they had a notable impact on published estimates for any specific geographic area below the national level.

The errors also affected two items that we estimate have small, but notable, impacts on national level estimates. The errors resulted in a small underestimate (approximately 1.5 percentage points) of grandparents responsible for caring for the their grandchildren for 5 or more years. In addition, the errors affected the service connected disability rating item, resulting in a small overestimate of the "Not Reported" category (approx. 1.9 percentage points) and small underestimates for the "30 or 40 percent" (approx. 0.7 percentage points), "50 or 60 percent" (approx. 0.4 percentage points), and "70 or more percent" (approx. 0.8 percentage points) categories.

Based on the analysis of the impact of these errors and the risks associated with correcting them, there are no plans to correct the dataset and re-release the affected data products.