Middle income-earners are moving out of San Francisco at a rate far outpacing those moving in.

The revelation, among those in a spate of new U.S. Census Bureau data, comes at a time of increasing concern over a growing Silicon Valley-created wealth gap in the city.

A net of about 5,075 individuals earning between $35,000 and $74,999 annually moved out of San Francisco between 2007 and 2011, according to Census Bureau data from those years. That number is about 40 percent more than the 3,654 people in the same income bracket that moved into the city during those years.

Large chunks of those middle income-earners departed the city for nearby Bay Area counties, including over a thousand to Alameda County just across the bay.

The data show that 43,864 people moved out of San Francisco to other California counties in those years, while 32,062 moved to the city from elsewhere in the state. In the same five-year period, 15,775 moved to San Francisco from out of state while 17,164 moved to a different state.

The data also show that those both coming and going from all Bay Area counties are widely scattered across the nation.

San Mateo County lost significant numbers of residents to Alameda and Contra Costa counties, but gained 5,440 from San Francisco.

Alameda gained a net of 3,156 residents from San Francisco, but lost 5,589 to neighboring Contra Costa. In Alameda, like San Francisco, more also moved to a different county in California than from one.

Contra Costa gained residents from every Bay Area county except Marin, Napa and Solano.

The Census Bureau data does not, however, portray an accurate portrait of the wealth moving into the city, with the highest income category capped at $75,000 and above.

A report released earlier this week by Joint Venture Silicon Valley found that those making $100,000 and up, about 45 percent of the region’s population, in recent years saw their incomes rise while those making up to $99,000 saw their incomes fall.