Before I could post a reasonable poll on the topic, I feel I would need more than my own case to be representative.
That said, I’d guess that my e-mail contents break down roughly this way:
1- Videos available on YouTube 60%
2- Jokes, riddles, trivia 20%
3- News stories worth discussing with sender 10%
4- Family matters 5%
5- News from sources I subscribe to 3%
I don’t get spam as such, since my provider blocks it. The unsolicited stuff that gets past that blocker is maybe the 2% I didn’t account for.
If you want to break yours down with more precision, please do. I’d expect to see at least a dozen categories of more-than-trivial e-mail issues.
I almost never get forwards anymore because “friends” just post them on Facebook these days.
Most of my emails are text messages from my daughter or notifications from Facebook. Gmail is really good with keeping spam in the spam box.
My email breakdown is very different then yours, I think:
Ads from companies I do business with (so not blocked by my spam filter): 50%
Emails regarding online purchases of various sorts: 25%
Family matters: 25%
I could probably get rid of a lot of the first category by unsubscribing, but I just don’t bother.
ETA: I just don’t get that many emails in total. Maybe 20 on a really busy day. Of course when I didn’t have spam filtering I used to get more than a hundred a day.