Thank you for posting in the HUD USER Forums. The HUD USER Forums provide a space for housing and community development researchers, academics, policymakers, and housing practitioners to interact with each other and discuss the material provided on HUD USER.
If you are interested in calculating different percentage income limits, according to a HUD economist, without knowing what the income limit is supposed to represent, it is unclear how it should be calculated. According to the HUD economist, we know for the Low-Income Housing Tax Credit program (LIHTC), which is supposed to be a 60 percent income limit, must be calculated based on the Very Low Income Limit (which represents 50 percent) multiplied by 120 percent. If, for example, the 120 percent income limits are supposed to be representative of the HUD Income Limits, then the Very Low Income Limits for those areas should be multiplied by 240 percent for the 120 percent income limit. However, this would vary from what is determined using the area median family income in areas where the Very Low Income Limit does not equal 50 percent of the Median Family Income (MFI) because of low or high housing cost adjustment, state minimum, hold harmless policies, or national average caps. According to the economist, because of these complications, you have to know how the regulation that calls for these income limits is written. For example, in HUD's Income Limits calculations, the MFI is used in the calculation of a 4-person household.
The Income Limits data set, along with further documentation on how they are calculated, can be found on the HUD USER website, here:
http://www.huduser.gov/portal/datasets/il.html.