A home affordability index of 100 means a median income family can barely afford a median-priced home, living paycheck to paycheck.

“The National Association of Realtors (NAR), which created the index, states that a value of 100 means a median-income family has exactly enough income to qualify for a mortgage on a median-priced home. This is based on the assumption that the mortgage payment (principal and interest) is no more than 25% of the family's gross income. The characterization of this as "barely afford" or "living paycheck to paycheck" is an interpretation, but it accurately reflects the financial situation of having just enough income to meet a lender's minimum qualification standard. Context: The NAR's Housing Affordability Index (HAI) calculation assumes the buyer can make a 20% down payment. An index below 100 means a median-income family does not have enough income to qualify for a mortgage on a median-priced home.”