John Maynard Keynes
Sir John Hicks, a Nobel laureate, created the model in 1937 as a graphical representation of the ideas introduced by John Maynard Keynes in his influential 1936 book, The General Theory of Employment, Interest, and Money. In his original IS–LM model, Hicks assumed that the price level was fixed, reflecting John Maynard Keynes' belief that wages and prices do not adapt quickly to clear markets.