We present a pricing kernel that summarizes well the main features of the dynamics of interest rates and risk in postwar U.S. data and use it to uncover how the pricing kernel has moved with the short rate. Our findings imply that standard monetary models miss an essential link between the central bank instrument and the economic activity that monetary policy is intended to affect, and thus we call for a new approach to monetary policy analysis. We sketch a new approach using an economic model based on our pricing kernel. The model incorporates the key relationships between policy and risk movements in an unconventional way: the central bank’s policy changes are viewed as primarily intended to compensate for exogenous business cycle fluctuations in risk that threaten to push inflation off target. This model, while an improvement over standard models, is considered just a starting point for their revision.

In this paper, I provide a possible explanation of why nominally risk-free bonds are essential in monetary economies. I argue that the role of nominal bonds is to serve as record-keeping devices in intertemporal exchanges of money. I show that bonds can only serve this role if they are illiquid (costly to exchange for goods). Finally, I show that in economies in which nominal bonds are essential, welfare and nominal interest rates are both positively associated with the supply of illiquid bonds (if that supply is small).

We analyze the setting of monetary and nonmonetary policies in monetary unions. We show that in these unions a time inconsistency problem in monetary policy leads to a novel type of free-rider problem in the setting of nonmonetary policies, such as labor market policy, fiscal policy, and bank regulation. The free-rider problem leads the union’s members to pursue lax nonmonetary policies that induce the monetary authority to generate high inflation. The free-rider problem can be mitigated by imposing constraints on the nonmonetary policies, like unionwide rules on labor market policy, debt constraints on members’ fiscal policy, and unionwide regulation of banks. When there is no time inconsistency problem, there is no free-rider problem, and constraints on nonmonetary policies are unnecessary and possibly harmful.

We study a model with heterogeneous producers that face collateral and cash-in-advance constraints. A tightening of the collateral constraint results in a credit-crunch-generated recession that reproduces several features of the financial crisis that unraveled in 2007 in the United States. The model can be used to study the effects of the credit-crunch on the main macroeconomic variables and the impact of alternative policies. The policy implications regarding forward guidance are in contrast with the prevalent view in most central banks, based on the New Keynesian explanation of the liquidity trap.

How much discretion should the monetary authority have in setting its policy? This question is analyzed in an economy with an agreed-upon social welfare function that depends on the randomly fluctuating state of the economy. The monetary authority has private information about that state. In the model, well-designed rules trade off society’s desire to give the monetary authority discretion to react to its private information against society’s need to guard against the time inconsistency problem arising from the temptation to stimulate the economy with unexpected inflation. Although this dynamic mechanism design problem seems complex, society can implement the optimal policy simply by legislating an inflation cap that specifies the highest allowable inflation rate. The more severe the time inconsistency problem and the less important is private information, the smaller is the optimal degree of discretion. As either the time inconsistency problem becomes sufficiently severe or private information becomes sufficiently unimportant, the optimal degree of discretion is none.

The desirability of fiscal constraints in monetary unions depends critically on whether the monetary authority can commit to follow its policies. If it can commit, then debt constraints can only impose costs. If it cannot commit, then fiscal policy has a free-rider problem, and debt constraints may be desirable. This type of free-rider problem is new and arises only because of a time inconsistency problem.

In standard approaches to monetary policy, interest rate rules often lead to indeterminacy. Sophisticated policies, which depend on the history of private actions and can differ on and off the equilibrium path, can eliminate indeterminacy and uniquely implement any desired competitive equilibrium. Two types of sophisticated policies illustrate our approach. Both use interest rates as the policy instrument along the equilibrium path. But when agents deviate from that path, the regime switches, in one example to money; in the other, to a hybrid rule. Both lead to unique implementation, while pure interest rate rules do not. We argue that adherence to the Taylor principle is neither necessary nor sufficient for unique implementation with pure interest rate rules but is sufficient with hybrid rules. Our results are robust to imperfect information and may provide a rationale for empirical work on monetary policy rules and determinacy.

The optimal choice of a monetary policy instrument depends on how tight and transparent the available instruments are and on whether policymakers can commit to future policies. Tightness is always desirable; transparency is only if policymakers cannot commit. Interest rates, which can be made endogenously tight, have a natural advantage over money growth and exchange rates, which cannot. As prices, interest and exchange rates are more transparent than money growth. All else equal, the best instrument is interest rates and the next-best, exchange rates. These findings are consistent with the observed instrument choices of developed and less-developed economies.

In this article, we analyze the implications of price-setting restrictions for the conduct of cyclical fiscal and monetary policy. We consider standard monetary economies that differ in the price-setting restrictions imposed on the firms. We show that, independently of the degree or type of price stickiness, it is possible to implement the same efficient set of allocations and that each allocation in that set is implemented with policies that are also independent of the price stickiness. In this sense, environments with different price-setting restrictions are equivalent.