PolicyMap calculates a Home Price to Income ratio using Black Knight’s home sale data and the IRS’s Statistics of Income (SOI) data. For each zip code, Black Knight’s median sale price for single family, condominium, and mobile homes is divided by the average adjusted gross income (AGI) reported in the SOI’s Individual Income Tax Statistics, producing a separate ratio for each property type. The result represents the number of years of average income needed to afford the median-priced home in a zip code. Zip codes with fewer than ten home sales in a year are suppressed.