"In the early 1950s Franco Modigliani, with Richard Brumberg and , formulated the life-cycle theory of consumption and savings that enjoyed a huge and undisputed success for at least three decades. It replaced Keynes’s ‘fundamental psychological law’ of savings, according to which the marginal and average propensities to save grow as income rises. On the other hand, the life-cycle theory maintains that the level of savings depends on the age of consumers, and hence on the demographic structure of society rather than on the level of family income."