This article[0] from almost 10 years ago estimated that the Google IPO resulted in 1,000 people having more than $5 million worth of Google shares.

So I guess it hinges on how you define "instrumental" and "almost none". It's a tautology to say that "instrumental" means "they contributed to the effort", so I would say "instrumental" means "it seems like no one else could have done it" and "almost none" means less than 5%. If you had to take a wild guess about Google, what percentage of that 1,000 would you estimate were instrumental? Furthermore, presumably there are more Google millionaires now, 10 years later. I wonder what percentage of those were also instrumental in Google's success?

[0] http://www.nytimes.com/2007/11/12/technology/12google.html