It really is more like the 99.99/.01 rule, but you get the idea. Better than 80% of the spam created is the work of just a few hundred spammers.
This goes to show you how unbelievably insecure the network is. While most of this spam originates at the 200 sources, it certainly isn’t all sent out by them – it is home PCs turned into spam-spewing zombies that take care of distribution.
I take it that is Windows PCs, as I haven’t heard anyone say otherwise (to date).