This commenter's tone is flippant but he brings up a really good question! Why do 9 mil people get benefits in a city of 10 million? I spent a few minutes googling "la population churn" until I realized that sociologists use the more polite term "turnover".

Between 1985 and 1990, the mean migration turnover rate was 35%.[1] And if you look at the map, LA county is shaded the color of 41-65% turnover. Let's guess 50%.

So if we guess 50% turnover per 5 years still applies between 2002 and 2010, then it's reasonable that 15million - 20million people have lived in LA county during that time period. Given that 49% of the US population get government benefits [2], this checks out. Especially since LA county has a higher poverty rate than the rest of the country. [3]

[1] Migration Turnover Rates in United States Counties [2006] http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=13...

[2] Census: 49% of Americans Get Gov’t Benefits; 82M in Households on Medicaid http://cnsnews.com/news/article/terence-p-jeffrey/census-49-...

[3] L.A. County leads California in poverty rate, new analysis shows http://articles.latimes.com/2013/sep/30/local/la-me-poverty-...