California dreaming? Hardly.

Mattresses on sidewalks, moving vans in driveways and hasty garage sales hint at a trend Bay Area residents have long suspected – exodus.

Real estate brokerage site Redfin released its annual "migration report" on Monday and found that those residing in San Francisco Metro are the most likely to leave. The catalyst for moving – high housing costs – should surprise no one.

"Movement of Bay Area residents to more affordable metro areas dominated the nation's migration patterns in the first quarter," the report states.

Analyzing a sample of 1 million Redfin users, the site found that 19.4 percent of potential homebuyers in San Francisco searched outside of the region for houses.

San Francisco also recorded the highest "net outflow" – the number of potential homebuyers looking to move to San Francisco Metro subtracted from the number of those who want to leave. The region's outflow was double that of New York.

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Sacramento was the most common in-state destination, while those heading out-of-state were most likely to settle in Seattle.

The median home value in San Francisco is $843,200, according to real estate site Zillow, while the average home cost in Sacramento is $293,600. In the past year, Sacramento's housing costs have risen by 11.3 percent.

"Even a Bay Area family with two solid incomes can struggle to afford a modest home," Redfin's chief economist Nela Richardson told the Marin Independent Journal. "For many, the only path to homeownership is to pack up and move out."

Jumping ship – a very, very expensive ship – for a cheaper locale is hardly unique to California. Across the nation, Redfin found that 19.8 percent of house hunters in 75 metro areas searched for houses outside their current cities.

Read Michelle Robertson’s latest stories and send her news tips at mrobertson@sfchronicle.com.