BTW, I don't know if it's everywhere in the US, but Mormon missionaries stopped knocking doors. The ones that last came to my house told me that (I don't count because I'm a member, so they come by unannounced sometimes).
My mission would have been so much easier if I didn't have to knock doors. 2 years of torture. We had a rule in our mission that we had to knock doors until 9:30 pm if we didn't have appointments...I served in the Bible belt. Do you know how pissed Baptists get when you knock on their door at 9:15 (not that I blame them)?