San Francisco is becoming a “Disneyland for yuppies.”

It’s urban flight flipped on its head: The number of low- and middle-income residents in San Francisco is shrinking as the wealthy population swells, a trend most experts attribute to the city’s exorbitant housing costs.

Many worry it’s increasingly turning San Francisco into an enclave of the rich, where nurses, firefighters, cops, teachers and other professionals aspiring toward homeownership or in need of cheaper rent can no longer afford to stay.

“A kind of derogatory term for the city would be Disneyland for yuppies,” said Hans Johnson, demographer with the Public Policy Institute of California. “There is a legitimate public policy concern when a city that many people have lived in for many years and regard as their homes becomes so expensive they can’t afford to live there anymore.”

This is merely the latest materialization of a long-term trend that has Americans leaving big-government, high-tax “blue” states in favor of smaller-government, smaller-tax “red” states.

One troubling (for conservatives) outcome of that trend is that many states that were once strongholds for Republicans are now becoming more purple than red as migrating liberals continue to support the politicians who support the policies they left behind in other states.  But the lesson to learn from the trend is this: In the marketplace of ideas, most people tend to “vote with their feet” for limited government and lower taxes.