How does HUD update median family incomes?
The FY 2010 MFI estimation relies on three-year American Community Survey (ACS) data (collected for 2006, 2007 and 2008). The manner in which the ACS data are used depends on the type of data available, which differs by place size. Local ACS MFI estimates are available for areas with populations of 20,000 or more, but the statistical reliability of these estimates differs. When local MFI estimates are available, HUD MFI estimates are based partly on local ACS estimates and partly on state-level ACS estimates. The higher the statistical reliability of local estimates, the more heavily they are used. Local ACS MFI estimates are used in inverse proportion to the size of their margins of error ratios (the numbers computed by adding and subtracting the published margins of error ratios, or MoERs, from the median family income estimates form the “90 percent confidence intervals” for the estimates. There is a 90 percent probability that any random sample of the same size from the population w
