Following a contractionary monetary policy shock, the aggregate output decreases over time for six to eight quarters, while the real interest rate increases immediately and remains high for three quarters, which can hardly be replicated by models characterized by a standard consumption Euler equation. This paper adopts a segmented markets framework where some households are permanently excluded from financial markets. The aggregate output and the nominal interest rate are modeled as exogenous autoregressive processes, while the real interest rate is determined endogenously. For intermediate levels of market segmentation, the model is able to account for both the persistent decreasing path of the aggregate output and the persistent increase in the real interest rate which follow an unanticipated increase in the nominal interest rate. The sign, the size and the persistence of the responses of the real interest rate and the money growth rate are close to those in the data.

This paper studies the effects of social insurance policies on efficiency and distribution of resources in a general equilibrium model of a closed economy with heterogeneous agents and repeated moral hazard. I compare optimal allocations in stationary recursive equilibria for economies with different guaranteed minimum consumption levels (social insurance). I show that the efficiency–equality trade-off associated with social insurance does not hold: Efficiency and inequality decrease as the minimum guaranteed consumption increases to around one third of the average consumption. However, if social insurance expands even further, the efficiency loss becomes very high and inequality increases.

We compare the numerical methods that are most widely applied in the computation of the standard business cycle model with flexible labor. The numerical techniques imply economically insignificant differences with regard to business cycle summary statistics. Furthermore, these results are robust with regard to the choice of the functional form of the utility function and the model's parameterization. In addition, the extended path approach, albeit time-consuming, and the Galerkin projection are found to be the most accurate methods, given that we have not used function approximations beyond the second degree.

We propose a model to study monetary policy under discretion. We focus on Markov perfect equilibria, ruling out trigger strategies. The model is simple enough that the determinants of monetary policy under discretion are clear. We also find that for all parameterizations with an equilibrium inflation rate around 2%, there is a second equilibrium with an inflation rate just above 10%. Thus the model can simultaneously account for the low- and high-inflation episodes in the U.S. experience.

We consider endogenous changes of inputs from labor to capital in the production of intermediate goods, i.e., a form of mechanization. We derive complementary relationships between capital accumulation and mechanization by assuming a Cobb–Douglas production function for the production of final goods from intermediate goods. A constant-elasticity-of-substitution production function in which the elasticity of substitution exceeds unity can be endogenously derived as the envelope of Cobb–Douglas production functions when the efficiency of inputs is assumed in a specific form. The difficulty of mechanization represents the elasticity of substitution.

This paper replaces increasing product variety with quality upgrading in the Romer model [Romer, Paul M., Journal of Political Economy 98 (1990), S71–S102]. We show that the range of parameters for which a steady state exists can be divided into two subspaces with well-behaved comparative statics and saddle-point dynamics in one subspace, but with “perverse” comparative-statics properties and either equilibrium indeterminacy or instability in the other subspace. These results for the closed economy can also be used to characterize the dynamics of the M-country open-economy version of the model.

We show that dependence on foreign energy can increase economic instability by raising the likelihood of equilibrium indeterminacy, hence making it easier for fluctuations driven by self-fulfilling expectations to occur. This is demonstrated in a standard neoclassical growth model. Calibration exercises, based on the estimated share of imported energy in production for several countries, show that the degree of reliance on foreign energy for many countries can easily make an otherwise determinate and stable economy indeterminate and unstable.

We study the conditions that guarantee equilibrium determinacy in a standard sticky price model augmented with a cost channel. A central bank that assigns some positive weight to the output gap in its reaction function makes the economy more prone to multiple equilibria relative to the standard case. The value of the threshold on the interest rate response to inflation is above one and depends on the fraction of firms that need to borrow their bills payment.