On first take, I'd put myself in top 10% and that's how I voted. After reflecting a bit, I think it's top 20% or lower. I think I'm regressing.
I was easily top 10% in my HS. I was top 25% in my college, and I have a masters degree in engineering from one of the top 5 schools in the country. That's why I voted how I did. But, I'm slipping. I know I am. I'm not nearly as fast as I once was, I start to struggle with some math that used to be simple, my memory is foggy. I don't know if it's aging or if I pickled too many brain cells, but I don't think I'm anywhere near as smart as I was 10-20 years ago.
That all being said, I can be pretty dumb too. I am socially awkward, sometimes I miss little details in movies that my wife has to explain to me, I tend to space out on lots of things. in terms of street smarts, I'm probably a solid C.
There are a lot of really not smart people out there. tons. If you don't believe me, go sit in the DMV for a while - you will leave there feeling like a super-genius.