The Census Bureau's American Community Survey, sometimes called the "snapshot of America," has all kinds of facts and figures about L.A. County. Among them (numbers rounded off):

-Population in labor force: 4.7 million
-Population not in labor force: 2.6 million
-Commuters who drive to work alone: 3.1 million
-Commuters who carpool: 500,000
-Commuters who take public transportation: 279,000
-Commuters who walk to work - 109,000
-Number of jobs in manufacturing: 560,000
-Number of jobs in arts, entertainment, recreation, accommodation and food services: 405,000 (I guess L.A. is not just about Hollywood after all)
-Number of households with incomes of less than $10,000: 274,000
-Number of households with incomes of more than $200,000: 148,000

Here's the page for the L.A. County results. The WSJ examines the overall results.