This is not a fair assessment. A big chunk of the direct marketing that results in actual sales comes from catalogs that people order and/or want -- I am not su

This is not a fair assessment. A big chunk of the direct marketing that results in actual sales comes from catalogs that people order and/or want -- I am not sure I would call that "spam". This type of direct marketing can be very cost efficient -- it's the old idea of selling more to people who are already your customers. As for the actual junky junk mail, I've seen 1-2% yields from well-designed programs (as others have mentioned). I've seen online campaigns (fb, adwords, amazon, etc.) with comparable yields.