How much spam you get depends on three main things, how many spammers know (or guess) your email address, how good your spam filtering is, and of course, how active the spammers are.
A couple of years back I investigated how spam volumes varied depending on the first letter of your email address (comparing firstname.lastname@example.org with email@example.com), with the variations almost certainly coming down to “guessability” (an email address of john@ is easier to guess than yvette@).
As to the impact of filtering, I investigated spam levels in the aftermath of the disabling of McColo — asking whether it was the easy-to-block spam that disappeared? The impact of that closure will have been different for different people, depending on the type (and relative effectiveness) of their spam filtering solution.
Just at the moment, as reported upon in some detail by Brian Krebs, we’re seeing a major reduction in activity. In particular, the closure of an affiliate system for pharmacy spam in September reduced global spam levels considerably, and since Christmas a number of major systems have practically disappeared.
I’ve had a look at spam data going back to January 2010 from my own email server, which handles email for a handful of domains, and that shows a different story!
It shows that spam was up in October … so the reduction didn’t affect how many of the spam emails came to me, just how many “me’s” there were worldwide. Levels have been below the yearly average for much of December, but I am seeing most (but not all of) the dropoff since Christmas Day.
Click on the graph for an bigger version… and yes, the vertical axis is correct, I really do get up to 60,000 spam emails a day, and of course none at all on the days when the server breaks altogether.