(NewsNation) — Higher mortgage rates and low supply sunk home sales to a nearly 30-year-low in 2023, and new research shows empty-nest baby boomers are sitting on much of the nation’s large home inventory.

Empty-nest boomers own nearly 30% of large U.S. homes. That’s twice as many as millennials with kids, who own just over 14% of the country’s big homes, a Redfin analysis found. Gen Z members with kids own practically none of those houses, just 0.3%.

Empty-nesters remaining in large homes is a relatively recent change. A decade ago, young families were just as likely as empty-nesters to own large homes, according to Redfin.

Population size doesn’t explain the homeownership difference. Millennials with kids own half as many large homes as empty-nesters, even though there are more millennials than baby boomers.

The report notes that older Americans benefitted from an abundance of newly built homes during the 1990s economic boom. Home values have grown four times faster than incomes over the last several decades, Redfin said.

“Housing has become really expensive because we are undersupplied. We built fewer homes in the 2010s than any decade going all the way back to the 1960s,” Redfin chief economist Daryl Fairweather told NewsNation Friday. “We really didn’t build for the millennial generation.”

Today’s real estate market has left baby boomers little incentive to sell. Even if they wanted to move, Fairweather said the smaller homes that empty-nesters might prefer aren’t readily available.

“We don’t build that mixed-use, walkable housing that has access to transit as much as we really should,” she said.

With today’s mortgage rates near 7%, baby boomers who downsize could end up with a nearly identical monthly payment.

But as mortgage rates come down, housing affordability is expected to improve somewhat over the next year, Fairweather said.

You can watch the full interview with Redfin’s chief economist in the player above.