Closely Related to the Overproduction Theory of the Business Cycle Is the Underconsumption Theory

Closely related to the overproduction theory of the business cycle is the underconsumption theory of the cycle. This theory has been put forward by Sismondi, Keynes, and others. Although the details may vary among supporters of this theory, the main claim is that when there is not enough consumptive spending in the economy, goods go unsold, workers are laid off, and businesses shut their doors. In other words, a depression occurs. One reason given why there is not enough consumptive spending is that capitalists might shift their spending from hiring workers to purchasing capital goods (i.e., substitute capital for labor). This means workers will be paid less and thus will allegedly not have enough money with which to consume all the goods produced. Whatever the reason given for the lack of consumption, the result is the same according to supporters of underconsumption theory: economic crisis and depression.

--Brian P. Simpson, Remedies and Alternative Theories, vol. 2 of Money, Banking, and the Business Cycle (New York: Palgrave Macmillan, 2014), 13.