Hawtrey contributed to a number of significant developments of economic analysis, including an original form of the cash balance approach to the quantity theory of money, to which he grafted an income approach, foreshadowing a treatment by John Maynard Keynes. He also advanced, as early as 1931, the concept of multiplier, which was given a central role by Keynes, and, indeed, Hawtrey played a significant role in the development of Keynes's thought in the years between his "Treatise" and "General Theory".