About 45,000 of California's 12 million households cumulatively earn 15 percent of the state's income, according to new tax return figures from the Franchise Tax Board.

Each of those households reported earning more than $1 million on their 2012 tax returns. Their ranks have grown for three consecutive years. And, since 2012 tax returns mostly cover income earned in 2011, the number of million-dollar earners has likely continued to increase as the stock market has risen.

Those wealthy households are most likely to live in the Bay Area. In Marin County, for instance, about 140 of every 10,000 households reported earning at least $1 million on 2012 returns, more than quadruple the statewide average of 30 per 10,000.

The Sacramento region is not a bastion for the rich. About 8 of every 10,000 households in Sacramento County reported earnings of at least $1 million on 2012 returns, roughly one-fourth the statewide rate. Placer, El Dorado and Yolo Counties had a rate twice as high, but still fall short of the state average.

The fortunes of the wealthy are still important in Sacramento because the state's income tax system is progressive. Though they represent 0.3 percent of the state's population and earn 15 percent of the state's income, those 45,000 households pay about 30 percent of its income tax.

This map shows the number of 2012 tax returns per 10,000 households in each county reporting more than $1 million in earnings. Hover over a mark to see data about a county.

Source: Franchise Tax Board
Note: Data not shown for counties where fewer than 10 households earned over $1 million.