That's probably some of it. I could be wrong but I think the ratios have gone up more than that. Anyway, I don't think the "techies don't click ads" effect is really as strong as a lot of people assume.
My guess is that (a) Google has optimized the ads for more clicks (b) advertisers have gotten beter at attracting clicks & (c) People are more aware of when to click on ads. If you're looking for a babysitter, you are more likely to have one booked ten minutes from now if you click an ad than an organic result. People have, consciously or unconsciously become aware of that and they click the ads when they want that kind of content.
