Also, the first thought I had was "what %age of adults are 18-30". Not that a 30yo should be dependent on their parents but I'd assume that people answering yes skew younger. And to your point about YC, that's also a young skewed demographic.
I also thought that YC might be younger, but then i remembered that most (successful) founders are 40+. Do we know something about YC demographics? Aside from the fact that it's obvious that a great many of them come from STEM fields. I did not find anything about it.