Affordability Index is a standardized measure that estimates whether a typical household in a given area earns enough income to qualify for a mortgage on a median-priced home under prevailing interest rate conditions.
Homeowners and buyers most often encounter affordability indexes when reading housing market reports, news coverage of real estate trends, or lender communications. The most widely referenced version is published by the National Association of Realtors, though regional variations exist. A score of 100 is generally considered the baseline, suggesting a household with the median income has roughly sufficient earnings to qualify for a median-priced home. Scores above 100 may indicate greater purchasing power in a market, while scores below 100 can signal that typical incomes are stretched relative to home prices. Because the index relies on assumptions about down payment size, prevailing mortgage rates, and income figures, actual affordability for any individual household will vary considerably. Interest rate changes in particular can shift the index quickly, sometimes within a single quarter.
- Watch for: Affordability indexes are backward-looking or based on snapshot data, so they may not reflect current rate or price conditions in fast-moving markets. Local indexes can differ meaningfully from national figures, so comparing both may give a more complete picture of a specific area.
Note: HomeRule provides this term for informational purposes only. HomeRule is not a lender, real estate agent, or financial advisor, and nothing here constitutes personalized financial or mortgage advice.
See also: Debt-to-Income Ratio, Mortgage Rate, Median Home Price