Using Lottery Effect to Make People Save. It's a great idea because it's motivating people to save by exploiting psychology: "I thought it was a good idea, because earning interest means you win anyway." This is a fallacy in a way, because "you win anyway" doesn't mean "it doesn't cost anything:" the cost of playing is the lower-than-usual savings rate, subtracted from a better rate you might get somewhere else by making the same investment. But players are unlikely to have saved money otherwise, and you lose more by not investing than by investing, so it's actually positive.