Mihai Andritoiu

As the country faces an affordability issue, there are dozens of factors that need to be considered to provide sustainable, manageable solutions. Here Americans migration patterns are shown to be dividing the country, attracted to jobs and the landscape. But with rising mobile work abilities, how will cities provide fair housing?

America's wealthy households are increasingly moving to coastal cities on both sides of the country, but those with more modest incomes are either relocating to or being pushed into the nation's Rust Belt, according to a new study.

That's creating "income sorting" across the country, with expensive cities like Los Angeles, New York and Seattle drawing wealthier residents. For instance, Americans who move to San Francisco earn nearly $13,000 more than those who move away, the study found. Conversely, those who are moving into less expensive inland cities such as Detroit or Pittsburgh earn up to $5,000 less than those who are leaving.

To be sure, gentrification – when the rich move in, pushing out the poor – is a well-known and long-standing trend that's impacted neighborhoods in cities such as New York. But the study from Dr. Issi Romem, a fellow at the Terner Center for Housing Innovation at the University of California, Berkeley, indicates gentrification may now be a national phenomenon.

The trend may not only hurt poorer residents who are forced out, but also the rich Americans who move to coastal cities. Well-off residents who move to already expensive cities like San Francisco are bidding up real estate prices until property becomes unaffordable for all but the very richest families. Many end up renting -- until that, too, becomes unaffordable.

Why the allure of the Atlantic and Pacific coasts? Most coastal cities like Boston are now highly desirable due to university access and high-tech jobs. But their close proximity to water means they are running out of room for construction.

The coastal "in-migrants"
The wealthy people who are moving to the coasts, or what the study calls "in-migrants," are often young, highly educated professionals who want to rent rather than buy. They are also typically multi-income households with roommates.

When people start families, they tend to leave those expensive cities. For instance, Sacramento has fewer earners per household among in-migrants "because it is a key destination for those leaving the San Francisco area in search of cheaper housing," Romem said.

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