In his classic work Keynes had said that depressions result from inadequate aggregate demand :Production and employment fall below their potential ,when households , firms , and the government together are not spending enough to keep everyone working .

• 凯恩斯在他的经典著作中说过，经济萧条是由于总的需求不足导致的：当家庭、公司和政府部门的全部消费都不能保证每个人都有工作的时候，生产率和就业率就会低于潜在的水平。