Almost all of it. LA County does have the entertainment, but it's also a major port. And several high tech companies are there. (you'll see this as a trend, turns out liberals get tech degrees and create technology too). New York county has New York in it, so that's going to be Wall Street. Harris County (Houston), the 3rd largest county by GDP, is in Texas. That's generated by aerospace (General Electric), several computer companies like HP, and of course the Oil Industry. Cook County (Chicago) is #4 on the large economy counties. There are several healthcare companies and insurance agencies headquartered there. And a great deal of shipping still goes through Chicago. Orange County is #5, and the primary employment industry is high tech.