By Matt Phillips
Quartz
February 25, 2015
Economists have long theorized about why people save. The most-famous theory, the so-called “life-cycle” theory of savings put forward by Nobel Prize-winning economist Franco Modigliani in the 1950s, said—to put it crudely—that people save when they’re young to finance their lives when they’re old. It sounded reasonable. And it was hugely influential for decades.