 In underconsumption theory in economics, recessions and stagnation rise due to inadequate consumer demand relative to the amount produced. It means that there is an overproduction and a demand crisis. The theory forms the basis for the development of Keynesian economics and the theory of aggregate demand after the 1930s. Underconsumption theory narrowly refers to heterodox economists in Britain in the 19th century, particularly 1815 onwards, who advanced the theory of underconsumption and rejected classical economics in the form of Ricardian economics. These economists did not form a unified school, and their theories were rejected by mainstream economics of the time. Underconsumption theory is an old concept in economics, going back to the 1598 French mercantilist text led tracers yet richesus por metterlos dot hen splendor the treasures and riches to put the state in splendor by Barpe-Elemy de Lafimus, if not earlier dot one. The concept of underconsumption had been used repeatedly as part of the criticism of Seyslaw until underconsumption theory was largely replaced by Keynesian economics which points to a more complete explanation of the failure of aggregate demand to attain potential output, i.e., the level of production corresponding to full employment. 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.