Many types of scarcity are temporary and often discretionary, said Shafir, who is co-author with Mullainathan of the book, "Scarcity: Why Having Too Little Means So Much," to be published in September. For instance, a person pressed for time can reschedule appointments, cancel something or even decide to take on less.
"When you're poor you can't say, 'I've had enough, I'm not going to be poor anymore.' Or, 'Forget it, I just won't give my kids dinner, or pay rent this month.' Poverty imposes a much stronger load that's not optional and in very many cases is long lasting," Shafir said. "It's not a choice you're making — you're just reduced to few options. This is not something you see with many other types of scarcity.