Google vs. the others

We know google owns the search market, but we wanted to find out just how much they own for ourselves. We took a random sample of 30 or so sites we are running analytics on in various industries and the outcome was a little more google heavy than anticipated.
Total Search Engine Traffic: 31,933 hits (last 30 days)
Google: 78%
Yahoo: 15%
Bing: 7%
Red Olive SEO