CEVAP:

The views of the classical model which guarantee full employment equilibrium were began to be questioned as a result of the long-term economic stagnation and the associated high unemployment during Great Depression that occurred in the 1930s. In order to solve this problem, British economist John Maynard Keynes argued that the
economic equilibrium, as put forward by Classical economists, does not mean that the level of full employment income is provided at the same time. According to Keynes, equilibrium income can be achieved at the level of underemployment or overemployment.