The housing market faces its biggest test yet

So far, nothing has done much to slow down the housing market.

But the red-hot housing market now faces its biggest test yet: Soaring mortgage rates.

Over the past 12 weeks, mortgage rates have posted their largest jump since the ’90s. As of March 24, the average 30-year fixed mortgage rate stood at 4.42%—up from 3.11% in December. And it isn’t over yet: Industry insiders tell Fortune it’s likely to go higher this week.

When the pandemic struck two years ago, the Federal Reserve quickly put downward pressure on mortgage rates. By the summer of 2020, the average rate was below 3%. The enticement of record low mortgage rates encouraged more buyers to jump into the market. As home prices soared, those low rates also helped to alleviate some of the burden for homebuyers. But as mortgage rates rise, it will have the opposite effect: Higher rates will increase buyer’s borrowing costs at a time when they’re already stretched thin by record home price growth. Simply put: This swift move up in mortgage rates amounts to an economic shock.

“If rates rise above 5% you will price buyers out of the market,” Devyn Bachman, vice president of research at John Burns Real Estate Consulting, tells Fortune. “The higher rates could also discourage investor activity, which accounts for a large portion of home sales today.”

The impact higher rates has on the housing market, Bachman says, was made very clear in 2018. Back then, the market lost some steam after mortgage rates jumped one percentage point.

To see why spiking mortgage rates put downward pressure on a housing market, just look at buyers’ monthly payments. If a borrower takes out a $400,000 mortgage at a 3.11% fixed rate, they’d owe a monthly payment of $1,710 over 30 years. At a 4.42% rate that payment climbs $2,008. But if rates do climb to 5%, that mortgage payment becomes a whopping $2,147. That’s a lot to stomach—especially when considering they’re shopping in a market where U.S. home prices are up 18.8% over the past year.

Of course, higher rates also means some borrowers (who must meet banks’ strict debt-to-income ratios) will lose their mortgage eligibility. Fewer buyers, in theory, should translate into fewer bidding wars.

In the eyes of Logan Mohtashami, lead analyst at HousingWire, we should root for rising mortgage rates to pull some steam out of what he considers a “savagely unhealthy” housing market. The current rate of home price growth isn’t sustainable: Simple economics dictates it can’t outpace income growth forever.

“Everyone should embrace higher rates to cool off this madness, and hope inventory rises,” Mohtashami tells Fortune.

If cooling does come, Mohtashami says, we’ll first see it in the monthly inventory numbers. So far, that hasn’t happened. In fact, inventory levels in February dropped once again. That lack of supply leaves home shoppers to choose between bidding well above asking price or remaining a renter.

Even if rising mortgage rates do cool the market a bit, it doesn’t mean prices will fall. In fact, forecast models still have home prices going higher this year. Between February 2022 and February 2023, Zillow forecasts prices will rise 17.8%. Meanwhile, CoreLogic predicts year-over-year price growth will slow to 3.8% by January 2023.

How could home prices continue to tick up in the face of soaring mortgage rates? Demographics. As Fortune has previously reported, we’re still amid the five-year window (between 2019 and 2023) when every millennial born in the generation’s five largest birth years (between 1989 and 1993) will hit the all-important first-time homebuying age of 30. The supply side of the housing market, which saw a decade of under-building following the Great Recession, simply can’t match all that demand. In total, Freddie Mac says the nation is under-built by around 4 million homes.