Be careful about the slice and dice effect. Depending on how you divide up the numbers you can make any thing come out on top. In some sense the problem is a lot worse. Its not just spam, worms, viruses. Its not just residential broadband users. Its not even just Microsoft Windows.

while i agree, i think something i said earlier needs to get re-said:

...

So-called "broadband" user populations (cable, dsl, fixed wireless, mobile wireless) are full time connected, or nearly so. They are technically unsophisticated, on average. The platforms they run trade convenience for security, and must do so in order to remain competitive/relevant. Margin pressure makes it impossible for most "broadband" service providers to even catalogue known-defect customer systems or process complaints about them.

Those facts are not in dispute. [...]

so, we know that a "broadband customer netblock" operator will not handle complaints, will not fix the systems that are known to be running third-hand malware, and that the only recourse against abuse from those places is blackholing them one (ipv4) /32 at a time, or blackholing them all at once and forcing mail servers (whether legit or not) to operate from a higher-rent neighborhood. there's no choice at all, really.