The review of the 2007 operational data discovered evidence that suggests a high incidence of misclassification of uninhabitable units as vacant units. The effect of misclassification was almost entirely removed through a modification in the weighting methodology for Orleans and St. Bernard Parishes. The effect of the weighting adjustment was to down-weight units that had the vacancy status of "Other Vacant". This modification resulted in more consistent and accurate ACS estimates of the number of vacant units and "persons per household" in these two parishes. This modification was also made to the 2006 ACS weighting methodology.