One of the most important studies of economic history is General Theory of Employment, Interest and Money written by John Maynard Keynes in 1936. Keynes has developed an economic theory for explaining complex economic events by using the information about markets and behaviors in these markets. Therefore, the origins of macroeconomics are widely based on Keynes’ book and theoretical breakthrough attributed to him is often called as the “Keynesian Revolution”. Keynes refused the idea that the employment was determined by prices and wages as put forward by classical models and developed the opinion that the aggregate demand for goods and services produced in the economy was the main factor determining the employment.