If hope and fear don’t guarantee compliance, there’s always embarrassment. Vampire bats are famous for their willingness to regurgitate a blood meal to feed fellow bats that are down on their luck. In fact, hiding one’s wealth is a problem. A fully fed vampire bat is as bloated as a fraternity water balloon, and the bats appear to rub bellies to see who is in a position to share. “It’s hard to cheat when your stomach is obviously distended.”-- from Taxing, a Ritual to Save the Species. Warren Buffet's secretary would surely approve.
Fig 1. Social democracy, with teeth