Some of Becker's most compelling research concerned altruism. He argued, for instance, that the same person who might be purely selfish in business could be exceedingly altruistic among people he knew--although, importantly (Becker is an economist, after all), he predicted that altruism even within a family would have a strategic element. Years later, the economists Doug Bernheim, Andrei Shleifer , and Larry Summers empirically demonstrated Becker's point. Using data from a U.S. government longitudinal study, they showed that an elderly parent in a retirement home is more likely to be visited by his grown children if they are expecting a sizable inheritance. But wait, you say: maybe the offspring of wealthy families are simply more caring toward their elderly parents? A reasonable conjecture--in which case you'd expect an only child of wealthy parents to be especially dutiful. But the data show no increase in retirement-home visits if a wealthy family has only one grown child; there need to be at least two. This suggests that the visits increase because of competition between siblings for the parent's estate. What might look like good old-fashioned intrafamilial altruism may be a sort of prepaid inheritance tax. Some governments, wise to the ways of the world, have gone so far as to legally require grown children to visit or support their aging moms and dads. In Singapore, the law is known as the Maintenance of Parents Act. Still, people appear to be extraordinarily altruistic, and not just within their own families.