Probably a similar number if you looked at it as an actual percentage of new companies. My next door neighbor is the founder of a little company called Garmin. Cerner was also founded here.

That changes the negotiating perspective of the job seeker. If you're surrounded by a rather large number of companies in that range - http://graphics.wsj.com/billion-dollar-club/ - and are skillful enough to enjoy offers from multiple suitors, you're bound to do your analysis, perhaps employing some backchannel communication.

If the theoretical maximum of company exit is in single millions, then spending time negotiating 0.25% vs 0.3% equity package is meaningless.

For better or for worse, those chances actually are related, because the #1 source of >$1BB exits is being acquired by other billion dollar tech companies, most of which are heavily networked in SV.