Act Consequentialism and Inefficacy

A variety of eating and purchasing practices, in particular vegetarianism, are often motivated via an appeal to their expected good consequences. Lurking in the background, however, is the question: can I really hope to make a difference via my purchases in a social world as complex and wasteful as our own? I review the evidence as it stands and conclude that there are good reasons to suspect that one probably does not make a difference directly via one's purchases. That said, there may be some related, though less direct, reasons to be vegetarian.