Seems like a straight-forward question, except that it's not. Measured as a share of family income, poor people pay the most. Measured by the percentage of personal income tax, rich people pay the most - by far. From the California Budget Project:
The share of income that California's families spend on state and local taxes is a function of the state's relatively progressive personal income tax and regressive sales and excise taxes. Higher-income families pay a larger share of their income in income taxes. Lower-income families pay a greater share of their income in sales and property taxes. Families also indirectly pay a portion of the taxes imposed on businesses through higher prices and reduced corporate earnings. Higher-income families pay a greater share of the corporate income tax, whereas lower-income families pay a greater share of the sales and excise taxes paid by businesses.
All these facts and figures are important because of the possible ballot fight this fall over the raising of taxes. Gov. Brown is behind a measure that would raise income taxes on the very wealthy for the next five years, with the proceeds used to avoid making huge cuts in education funding. That might work when the economy is strong and those folks are making huge amounts of money, but it's a disaster during a downturn. Of course, there's another way to raise taxes and that's a proposal by Molly Munger that would raise taxes for everyone making over $7,300. The wealthier would have more of a burden, but most Californians would have a little skin in the game. As you might imagine, the Brown plan is far more popular.