Data is just data until it is parsed. Zillow, the Seattle-based online real estate site, is very good at collecting and parsing data. It has now parsed the numbers on out-of-market home searches and found that San Franciscans mostly search for homes outside of the area--while in much of the rest of the country, people are searching in San Francisco.

"San Francisco is one of the most popular housing markets searched by non-resident home shoppers on Zillow, yet many locals are searching for homes outside of the area," Zillow reports.

On average, a home in the San Francisco area gets more page views from afar than 92% of other markets. However, 50% of San Francisco-based views are of homes outside the area.

Why? The promise of success in hot job markets attracts people to places like San Francisco, but affordability may be a barrier to staying there long term, Zillow says. In the San Francisco metro, the median home value is just over $800,000 and the median rental payment is $3,400 a month.

The reverse is happening in booming Portland and Seattle markets. Both are highly desirable among outsiders and places where residents don't seem to want to leave. Homes in Portland get more page views from outside the area than 94% of other markets, while just 29% of views originating in Portland are of homes outside of the area.

"We look at home searches to get a read on people's housing aspirations and how they feel about housing and quality of life in their city, as well as their actual intentions to move into or out of a given area," said Zillow Chief Economist Dr. Svenja Gudell. "If someone lives in an expensive area, they may look for another place to live that is less expensive but offers a similar quality of life. Home shoppers in less expensive markets may weigh sacrificing space or cost in favor of a better job in a more expensive locale. Home search trends, in time, translate into actual moves and migration, which will have a lasting impact on the economy and landscape."

Search patterns in Austin are similar to those of San Francisco. On average, a home in Austin gets more page views from outside searches than 86 percent of other destinations, but more than half of Austin-based views are of homes outside the area. Home value growth in Austin is outpacing San Francisco's, up 9% over the past year.

Those who live in New Orleans, Miami and Detroit are looking for homes in other places, and few outsiders are looking to move in.

In Minneapolis, New York and Pittsburgh, most home shoppers are from within the area -- just 29% of current Minneapolis-area shoppers are looking elsewhere for homes.

In the chart below, Washington D.C. is shown with more people looking outside the market than inside, which correlates neatly with the impending changes owing to the presidential election.