As public-sector problems go, Idaho has a good one: too many people want to live there. According to Census Bureau data, Idaho is now tied with Nevada as the fastest-growing state in the union, in percentage terms. From 2010 to 2018, the state’s population grew by nearly 12 percent. The growth was concentrated in the state’s capital and largest city, Boise, which saw an 18.5 percent population increase over that period.

There’s a catch, however, at least in the eyes of many Idahoans: a disproportionate number of newcomers are coming from California. In the 12 months from July 2017 to July 2018, Californians accounted for nearly 60 percent of Idaho’s net migration. The state is far from alone in this regard. According to the U.S. Census Bureau, six of the seven fastest-growing states in the nation in percentage terms—Nevada, Idaho, Utah, Arizona, Washington, and Colorado—are in the West. In all six, California is the largest source of new residents.

None of this should be particularly surprising. With a population of approximately 40 million, it would be strange if California wasn’t the biggest supplier of expatriates—especially to nearby states. But far from making these demographic shifts unremarkable, California’s size comes with equally significant consequences for its neighbors. For while the number of departing citizens might seem like a rounding error for a state like California, they’re a significantly larger percentage of the population in the states to which they decamp. Nowhere is that felt more acutely than in Idaho, a mostly rural state without a major metropolitan area. (A “major” metro is generally defined as having a population of over 1 million; the Boise area has around 730,000.) Los Angeles County alone has more than five times as many residents as the entire state.

Predictably enough, this has fueled a backlash. As a recent report by Maria L. La Ganga in the Los Angeles Times notes, many longtime residents aren’t thrilled with the breakneck pace of change brought by California’s hordes. While La Ganga devotes a bit too much time to colorful but unserious signs of the blowback—a fringe Boise mayoral candidate, for example, who flippantly proposes erecting a wall to keep the Californians out—there’s no doubt that the deluge of movers creates genuine concerns. Median home prices in Ada County, where Boise is located, have increased by over 19 percent just since February 2018. Not only does the influx of Californians increase demand, but their inflationary influence is also compounded by housing budgets swollen by the sale of their Golden State properties.

As anyone who’s ever experienced one of these demographic surges up close will know, most local resentment is expressed in cultural rather than economic terms. (I once told a lunch companion in my adopted home state of Tennessee that I was originally from Southern California. His response: “I’m sorry to hear that.”) La Ganga quotes the diagnosis of Reverend Bill Roscoe, a California expat who’s been in Idaho since 2002: “If you come here and love it, everything’s fine. If you come here and fly that California flag in your driveway and have stickers on your car that say, ‘Santa Cruz,’ there’s going to be some hard feelings.”

That’s not an unreasonable position. Nor, it should be noted, is it an enforceable one. There’s no law that one can pass to uphold something as intangible as a community ethos, though that hasn’t kept people from trying—Wayne Richey, the fringe mayoral candidate, proposed higher property taxes for new arrivals in Boise. All the natives can really do is resort to the soft sanction of local norms. And that’s a harder task when the inflow is coming at such speed and volume that longtime residents’ influence is, as a proportional matter, waning.

The California-Idaho nexus presents an extreme version of the questions that all similarly situated places must answer: what do newcomers owe longtime residents? And how should the former treat the latter? On the major questions, the answers suggest themselves. Newcomers would do well to conduct themselves as converts rather than colonizers. It’s hard to welcome someone into a community that they seem intent on scrapping for parts. By the same token, locals have to concede that growth is inevitably accompanied by change. That can be uncomfortable—but much less so than the alternatives of stagnation or even decline.

On the everyday questions—the ones about how the parties actually come to a workable modus vivendi—the answers will surely be messier. But they will not be settled by public policy. Despite the occasional reveries that we’ll all sort into likeminded communities, most Americans don’t move for explicitly political reasons. So, there’s no easy way out: we’ll have to learn to live with one another. To do so, we’ll need to revive a virtue that modern America too often neglects: mutual forbearance. In Idaho, at least, they start with an advantage. The old-timers and the newbies already have at least one thing in common: neither wants to be in California.

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