Population shifts in America are often very specific, boiling down to nuances about policy, place and demographics--in other words, things besides just the weather. Certain metros, thanks in many cases to their ingrained attitudes, either decline or stagnate. And other metros, thanks to their attitudes, become receiving grounds for displaced populations. To name some macro examples, many people move from California to Texas, and from New York to Florida, because of their differing tax and regulatory policies. This occurs between cities, too, as many Chicagoans are, for similar reasons, moving to Atlanta and other "New South" cities.

Population shifts can also be intrastate phenomenons, with one example being in California. Certain policies that prevent Los Angeles from achieving livability for all have driven people to the state's Inland Empire, about 2 hours to the east.

According to Census figures, America's largest county-to-county population shift between 2007 and 2011 occurred out of Los Angeles County, and into San Bernardino and Riverside Counties, with 35,000 more people moving there than in the opposite direction. The L.A.-to-Inland numbers were even more stark between 2000 and 2006, sitting at a whopping 300,000. The Inland Empire is now one of the nation's fastest-growing economies as a result, and Riverside-San Bernardino-Ontario is now America's 13th-largest MSA, ahead of Seattle, San Diego and Denver.

Although it may be the case in some circumstances, this growth isn't because people are just dying to live in the Inland Empire. According to Trulia's real estate heat maps, the strongest demand throughout greater SoCal remains for land closest to the Pacific Ocean. Rather, a climate of Nimbyism and regulation in Los Angeles has--similar to how I described in a recent article about San Francisco—inflated housing prices and pushed people east.

To put a finer point on it: people who enjoy accessing the jobs, culture and geography of Los Angeles, but can't afford the housing there, instead "drive until they qualify," to the nearest locale that has a similar vibe at prices they can afford. Riverside, where median home prices are $350,000 (compared to $566,000 in L.A. County), and San Bernardino, where they are $253,000, both fill this need.

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"Los Angeles,” said USC demographer Dowell Myers to the Los Angeles Times,  “is a giant pump that pulls in people from other countries and all across America, then recirculates them." Living costs are a major reason why.

There are different types of areas from within the Inland Empire that migrants can settle. The counties of San Bernardino and Riverside extend east all the way to the Arizona border, meaning large stretches are remote desert. A lot of the land along their far western portion is old farms that have been subdivided into suburban tract housing. Even the two counties' namesake cities are very different.

One thing that makes California such an anomaly within America is that it's poorest cities are actually some of its fastest-growing. San Bernardino--along with Fresno and Stockton--is an example. The city went bankrupt several years ago, median household income there is $39,000, and the poverty level is 30%. The downtown area, and many surrounding neighborhoods, are run-down.

Riverside has historically been the wealthier of the two, having started as a hub for growing oranges. It has a thriving downtown, 4 separate colleges, and various tourist attractions, such as the historic Mission Inn. The median household income is $56,000 and only 17% live below the poverty line. This means it attracts different demographics than San Bernardino does from amid this great L.A. population exodus, and thus supports different industries.

“We have traditionally been a strong market in terms of logistics, distribution and transportation and construction,” said Rafael Guzman, the City's Director of Community & Economic Development, by phone. “That has been slowly changing to a more tech-based environment.” Another major employer is the tourism industry, suggesting that the city has a certain appeal beyond just the fact that it is close to L.A. and receiving its expats.

Nonetheless, the anti-growth climate within L.A. is the true driver here of the migration shift. Just as housing prices--read regulations--in San Francisco have pushed people out to Sacramento and Stockton, and in San Diego to south of the border in Tijuana, Los Angeles is pushing them to the Inland Empire, and other remote parts of SoCal.

[This article was originally published by Forbes.]