This [1] article stated that there are 350,000 Canadians currently living in SV. That's around 1% of our entire population. Considering most of these are members of a small minority of skilled software people (no idea what the exact percentage might be) it's likely to be pretty a huge chunk of the total.

It's a little surprising me how bad it is considering how much the Canadian government offers to tech startups (IRAP, SRED, etc.). However, the wages I see most established software companies paying let alone the startups probably has a lot to do with it. The lack of good software companies likely has more to do with the brain drain than anything else does.

[1]: http://www.theglobeandmail.com/report-on-business/rob-magazi...