In underconsumption theory, recessions and stagnation arise due to inadequate consumer demand relative to the amount produced. It is an old concept in economics, going back to Thomas Malthus if not earlier. The concept of underconsumption has been used repeatedly as part of the criticism of Say's Law 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, for example, the… (More on Underconsumption)