That would probably be a better strategy. But if you are looking at a naive, single variable, a prior purchase is the greatest single predictor of future purcha

That would probably be a better strategy. But if you are looking at a naive, single variable, a prior purchase is the greatest single predictor of future purchases. If you know nothing else about a person, the fact you purchased one post-hole digger makes it more likely you'll purchase another, as opposed to some random other internet denizen for which we know nothing. Having worked in email marketing analysis before, this effect was surprisingly robust across categories. It implies you are the kind of person that could use such a product - most people aren't.