Can’t find a house to buy? You can blame older Americans who don’t want to sell.

Nearly 40% of Baby Boomers, generally defined as people born between 1946 and 1964, have lived in the home they currently own for at least 20 years, while another 16% have been in their properties for 10 to 19 years, according to a report from real estate brokerage Redfin.

Previously older generations would downsize into smaller properties, creating more inventory for first-time buyers and young families. But today, more are choosing to age in place, at least until mortgage costs come down. And that’s the “driving force” behind a lack of available properties that has made it difficult for many potential buyers to crack into the market.

Currently, the typical US homeowner has spent nearly 12 years in their house — roughly twice as long in 2005, but down slightly from the peak of 13.4 years in 2020, according to Redfin.

That was right before the pandemic set off a US housing frenzy that was fueled by low interest rates. But as surging mortgage costs cooled the market, many homeowners have been reluctant to sell their properties. That’s fueled an inventory shortage that has buoyed home prices, even as many potential buyers wait for borrowing costs to come down.

For many older Americans, staying put makes financial sense. More than half of Baby Boomers own their homes outright, according to Redfin. And with mortgages rates still well north of 6%, those that are still making monthly payments are reluctant to move and take on a much higher borrowing costs than what they’re currently paying.

Existing homes account for more than 90% of all home sales in the US, and the lack of available properties has been particularly hard on first-time buyers, according to Chen Zhao, the head of economic research at Redfin. It’s also squeezed growing families who are left renting or looking for newly constructed properties.

“When baby boomers hold onto their homes, which are often larger family sized homes, they create a shortage of homes for younger families who are trying to buy their first home or move up to a larger house,” said Zhao. “Without that, younger families are facing both high rates and high prices, worsening an affordability challenge that already plagues the market.”

This article was provided by Bloomberg News.