Professor Kiyotaki has made several outstanding contributions in the areas of macroeconomics and monetary economics by creating innovative original models and, thereby presenting new insights to old questions` First, he provided a new justification for active monetary policy by formulating a macroeconomic model based upon monopolistic competition, where monetary policy plays a role of coordinating activities to choose an equilibrium with higher output.

Second, he constructed a search-theoretic model of money where fiat money serves as a medium of exchange for multilateral exchange, where people accept money not because it is required by a technical reason (e.g. by cash constraint) but simply because they believe others would accept money as well, Third he formulated a model with credit contracts with limited enforcement where land plays two distinct roles: the role of collateral for debt and the role of a productive input. In such an economy, the level of credit limit to each firm positively depends upon the value of land, while the credit provided to each firm stimulates the demand for land.