To analyze the affordability and availability of Pennsylvania’s rental housing stock, we used special tabulations of the decennial census data called comprehensive housing affordability strategies (CHAS) data. The most commonly used measure to assess rental housing supply is the vacancy rate. Yet, vacancy rates do not indicate if an available unit is in adequate condition. While this study provides vacancy rates for each area analyzed, it does not focus on these data as the primary indicator of rental housing supply. Instead, this study gives more weight to measures of shortages of affordable housing that can be calculated from CHAS data, as defined in the next section.