Underconsumption is a theory in economics that recessions and stagnation arise from an inadequate consumer demand, relative to the amount produced. In other words, there is a problem of overproduction and overinvestment during a demand crisis. The theory formed the basis for the development of Keynesian economics and the theory of aggregate demand after the 1930s. One of the early underconsumption theories says that because workers are paid a wage less than they produce, they cannot buy back as much as they produce. Thus, there will always be inadequate demand for the product.