The U.S. housing deficit grew to nearly 4.7 million homes in 2023, according to a report from Zillow, based on recently released data from the U.S. Census Bureau.

The deficit in homes available increased by 159,000 year over year in 2023, as the total supply increased by 1.4 million, which wasn’t enough to meet the demand from the estimated 1.8 million new families formed each year. Zillow writes that the housing deficit is a “prime driver” of the nation’s housing affordability crisis.

According to data from the U.S. Census Bureau, about 3.4 million homes sat vacant and were available for rent or sale in 2023. At the same time, an estimated 8.1 million families shared their homes with unrelated people. Zillow writes that while some people choose to live with roommates, most of these families would probably prefer to have their own homes, if they could afford to do so.

Millennials represent the largest generation of people sharing homes with non-relatives. Even though mortgage costs are slightly lower than last year nationwide, buying a home is still a stretch, especially for first-time buyers.

Zillow writes that a family earning the median household income could afford to buy a typical home in 2019. But not today. Families need to earn nearly $100,000 a year (which is $17,670 above the median household income) to afford the typical U.S. home worth $367,969. That assumes they have $73,594 saved for a 20% down payment.

“The unfortunate fact is that we still don’t have enough housing in this country for people who need it. Construction has helped prevent the housing deficit from ballooning, but it hasn’t yet begun to close the gap,” said Orphe Divounguy, senior economist at Zillow. “We know what works: lower building restraints to allow for more density and less expensive housing. More of these measures at the local level can help get more homes built and begin to ease this outsize financial burden for millions of Americans.”