We all know people moved during the pandemic; with a newfound ability to work from anywhere, many migrated to the Sunbelt. Between April 2020 and July 2023, Census Bureau data shows the population in the South rose by nearly 4 million people.

But the real story, according to a Bank of America research note released Monday, is what’s happening in the West.

“While this rise is sometimes discussed in the context of the pandemic, in many ways it is not new ‘news’—the South’s share of U.S. population has been rising for a long time,” the bank said. “The real story, arguably, is the decline in the share of population of the West … Its share of overall U.S. population has flattened, and now appears to be falling.”

For the first time since World War II, the share of Americans living in the West has fallen.

Bank of America’s data reveals population growth across major metropolitan areas in the West is declining compared with the prior year, with Las Vegas being the exception. “The fall in population growth in the West is more of a Pacific story,” the bank said—with a chart showing declines in population growth across San Diego, Portland, Seattle, Los Angeles, and San Francisco, with the latter two cities leading the declines.

But why are people giving up on the West Coast, and maybe even their dreams of living in California? It’s simple: housing costs.

“We believe relative housing affordability remains a key part of the story,” the bank said. Major metropolitan areas with higher median mortgage payments have experienced negative population growth or, at best, weakly positive growth annually, according to Bank of America.

“Looking at the [metropolitan statistical areas] in the Pacific states in the West, they all tend to have higher-than-average mortgage payments relative to the U.S.,” the bank said. “By contrast, in the southern Mountain states, mortgage payments are lower than the U.S. average, so outward migration is potentially a reaction to housing costs.”

San Francisco and Los Angeles experienced the largest population losses, while San Antonio and Austin saw some of the biggest increases. In terms of housing costs, it’s not difficult to understand why that is. The average home value in Los Angeles is $918,087; in San Francisco, it’s $1,216,087. Meanwhile, the average home value in Austin is $527,205. In San Antonio, it’s just $251,545, per Zillow.

Let’s do the math: The monthly mortgage payment on, let’s say, a million-dollar home after putting 20% down at a 7% 30-year fixed mortgage rate (not including taxes and insurance) would be around $5,300. That’s a lot more than what you’d typically pay living in San Antonio or Austin.

The relationship between migration and housing costs is not perfect: Phoenix’s population, for instance, fell slightly over the past year, despite the fact the city does not have relatively high mortgage payments. But the metropolitan population is up substantially compared with the first quarter of 2020, which suggests “relative housing costs do exercise some ‘gravitational pull’ on population flows, even if shorter-term factors also make an impact.”

Over time, Bank of America expects domestic migration flows across the country “to lead to some ironing-out in relative housing costs” among the metropolitan areas losing residents. The bank believes it’s likely those regions would see reduced pressure on home prices and rents, which would eventually equate to cheaper housing costs—although, that’s in comparison to areas currently seeing spikes in their population growth.

“Interestingly, our data also shows a relatively high proportion of higher-income households in the outflow of people from [metropolitan statistical areas] in the West to the South, which could boost demand for housing in southern [metropolitan statistical areas] by more than a straightforward count of the people leaving would suggest,” the bank said. “Likewise, the West may find demand for housing weakening more if higher-income households are leaving.”

More than 40% of people leaving the West for the South had incomes above $125,000, and over 10% had incomes above $250,000. Even so, the bank’s data found that a higher proportion of those leaving the West are one-person households. It’s mostly single-person households leaving Los Angeles and San Francisco. So if we assume they’re flexible to changes in the economy, they might return eventually.

“Overall, as the pandemic itself fades as an influence, whether the internal migration flows we have observed in Bank of America internal data will continue or ease is an open question,” the bank said. “While current patterns may seem entrenched, over time, we think relative housing cost adjustment is likely to have an impact.”