Would-be U.S. homebuyers face an increasingly daunting task, as homes were less affordable in May than they have been in about 15 years, according to the latest National Association of Realtors Home Affordability Index.

The national index dropped to 102.5 in May, the lowest it has been since July 2006, when it stood at 100.5. The current index also was close to July 1990, when it came in at 100.2. Both of those periods were characterized by rising home prices and high interest rates.

NAR formulates the index based on median existing-home prices, median family incomes and average mortgage rates. An index above 100 means that a family with the median income had more than the income required to afford a median-priced home, so a higher index means more affordability, on average, for more buyers.

Also, the organization reports, first-time buyers now spend an average of 25.6% of their family income on mortgage payments, pushing over the threshold into unaffordability. NAR defines a mortgage as affordable if the payment amounts to 25% or less of a family’s income.

Rising interest rates, combined with rising prices, have made U.S. houses less affordable, especially when compared with 2020 and last year, the organization reports. In May 2021, the index stood at 148.2.

The rate for 30-year mortgages came in at 5.31% this May compared to 3.01% a year earlier, NAR reports. Also, median existing-home sales price rose 14.6% from May 2021.

“I don’t know that we’ll ever see affordability again like we saw in the last year or two,” First American Financial Corp. Chief Economist Mark Fleming told The Wall Street Journal.