It is an impressive margin, but it's a city-limits game. Note LA+SF=13, but there are 51 in CA, almost all of whom are in those two metro areas. Houston+Dallas=41 out of 64 Texas, and most of those missing 23 are in the Metroplex, including #1 Exxon (although I think Houston metro still comes out ahead overall). But Houston does deserve a lot of kudos for managing to keep almost all of its metro F500s inside the city limits and contributing to the tax base. I think that can be chalked up to aggressive annexation, no zoning (allowing multiple skyscraper job centers, inc. dt, uptown, TMC, Westchase, Energy Corridor, Greenspoint, etc.), and strong freeway construction/expansion allowing employees in the far suburbs to have reasonable commutes to the core.