This working paper presents analysis of custom tabulations of the 2006-2010 American Community Survey (ACS), known as the "CHAS data." The CHAS data combine ACS microdata with HUD adjusted median family incomes (HAMFI) to create estimates of the number of households that would qualify for HUD assistance. These data are used to estimate the number of rental units and ownership units that would be affordable and available to a prototypical household at specified income levels. The analysis discusses affordability for the United States as a whole, and for three local jurisdictions. The data indicated that there is a severe shortage of housing affordable and available to low- and very low-income households—particularly in the ownership market.