I have no idea. But I can tell you that any American graduating from a major school with an engineering degree is being snapped up by the high tech industry, and not just Apple. We can’t mint engineers here fast enough.
You say Forbes attributes 257,000 jobs, direct and indirect to Apple. Here's a link to a story I was given yesterday where Apple is claiming over a million.
Trying to get to the bottom of exactly how many jobs Apple has actually created for American workers seems to dead end at "It's HUMONGOUS, so shut up!"