Well, for a 30-day period, ending today, I deleted no spam/phishing emails on my Gmail account. Total after a month is 759, or an average of 25.3 spams a day.
I received 825 valid emails in that same period, or roughly 27.5 per day. So, spam made up 47.9% of email entering my Inbox in the last month.
While I'm appalled at the 759 number, I'm actually surprised it's below 50% -- I had expected higher.
And Gmail's spam filter works quite well. I'd estimate that only roughly 50 of the 759 spam messages, about 7%, weren't appropriately flagged and filed automatically.
Thanks, Gmail.
Just over 4500 spam messages in my Gmail spam folder in a month here.