ACS-1 areas are FMR Areas which have at least 200 sample cases of two-bedroom standard quality rents. ACS-1 areas may be MSAs, subareas that are assigned CBSA base rents, subareas that have their own base rents, or large nonmetropolitan counties.
ACS-2 areas are FMR Areas which are subareas of CBSAs where the subarea is not assigned the CBSA rent, and the subarea does not have at least 200 sample cases of two-bedroom standard quality rents, the CBSA containing the subarea does have at least 200 sample cases of two-bedroom standard quality rents and at least one area within the CBSA has its FMR based on the CBSA rent.
ACS-3 areas are FMR Areas which are MSAs, subareas, or nonmetropolitan counties that have fewer than 200 sample cases of two-bedroom standard quality rents.
ACS-4 areas are FMR Areas that have at least 200 sample cases of two-bedroom recent mover rents where the recent mover estimate is statistically different from the standard quality updated rent. ACS-4 areas may be entire MSAs, subareas assigned CBSA base rents, other subareas, or large nonmetropolitan counties. By definition, these areas are a subset of ACS-1 areas.
In ACS-1 FMR areas, the update factor used to generate the June 2006 value is the ratio of the 2006 ACS two-bedroom standard quality rent to the 2005 ACS two-bedroom standard quality rent for the FMR Area.
In ACS-2 FMR areas, the 2005 ACS to 2006 ACS update factor is either (1) the ratio of the 2006 ACS two-bedroom standard quality rent to the 2005 ACS two-bedroom standard quality rent for the CBSA containing the FMR Area, or (2) the ratio of the 2006 ACS two-bedroom standard quality rent to the 2005 ACS two-bedroom standard quality rent for the entire state, or population weighted average change of states, containing the FMR area, whichever brings its 2006 updated rent closer to the value of its CBSA's 2006 updated rent. For FY 2009, we discontinued selecting between CBSA and state based update factors for subareas which are part of a CBSA for which no part of the CBSA uses the CBSA rent. Where the rents for subareas within a CBSA were so disparate that none of them resembled the rents for the whole CBSA, underlying economic conditions are also expected to be significantly different. Moving these subarea rents towards a CBSA rent that no subarea used did not appear to be contributing to accuracy in rents for these subareas. These subareas have been made ACS-3 areas and use a state-based change factor.
Two different population-weighted state average changes can be produced for subareas that cross state lines - the relevant state populations of the subarea and the relevant state populations of the CBSA. Where this is the case, in keeping with the ACS-2 FMR area policy of nudging subarea rents towards the CBSA rent, the population-weighted state change that brings the subarea closer to the CBSA is used when the state change is used instead of the CBSA change as outlined above.
In ACS-3 FMR areas, the 2005 ACS-to-2006 ACS update factor is the ratio of the 2006 ACS two-bedroom standard quality rent to the 2005 ACS two-bedroom standard quality rent for the entire state containing the FMR area, or a population-weighted average of states specific to the FMR area.
In ACS-4 FMR areas, the local 2006 ACS recent mover rent becomes a new base rent for 2006 if the updated 2005 ACS-generated rent is outside its 90 percent confidence interval and the recent mover rent is greater than the local standard quality rent. This means the 2006 ACS is used to replace the updated 2006 base rent with a 2006 local ACS base rent. If the statistical criteria are met and the standard quality rent is higher than the recent mover rent, the standard quality rent estimate is used.