I suppose you could look at a number of successful companies, where they started out, and where they eventually got funding.

I'm pretty sure you'll see lots of companies starting outside SV, moving to SV to get funding, and then succeeding.

These numbers would be interesting.

Unfortunately, there's a confounding variable: people know SV is a good place to start a startup (even if they aren't as sure as pg), so more startup starters will start up there, anyway.

Those that moved to SV compared to those that didn't is still an interesting metric.

I'd go much simpler: time from searching for funding to closing a round.