Actually, I was quite interested to notice recently that I don't seem to get that much spam any more. There are apparently only 16 emails in my spam folder from the last 30 days. I'm not particularly careful with my email address either.
What I have noticed, however, is that I am now getting more and more telemarketing phone calls (robo calls) on my cell phone than I am spam hitting my inbox. It's reached the point where I keep my phone on silent all of the time because I get 5+ robo calls each day.
Unless Google is automatically deleting stuff it's really sure about straight away?