TIME TO BUILD AND AGGREGATE FLUCTUATIONS
BY FINN E. KYDLAND AND EDWARD C. PRESCOTT 1
The equilibrium growth model is modified and used to explain the cyclical variances of a set of economic time series, the covariances between real output and the other series, and the autocovariance of output. The model is fitted to quarterly data for the post-war U. S. economy. Crucial features of the model are the assumption that more than one time period is required for the construction of new productive capital, and the non-time-separable utility function that admits greater intertemporal substitution of leisure. The fit is surprisingly good in light of the model’s simplicity and the small number of free parameters.
THAT WINE is NOT MADE in a day has long been recognized by economists (e.g., Böhm-Bawerk ). But, neither are ships nor factories built in a day. A thesis of this essay is that the assumption of multiple-period construction is crucial for explaining aggregate fluctuations. A general equilibrium model is developed and fitted to U. S. quarterly data for the post-war period. The co-movements of the fluctuations for the fitted model are quantitatively consistent with the corresponding co-movements for U. S. data. In addition, the serial correlations of cyclical output for the model match well with those observed.
Our approach integrates growth and business cycle theory. Like standard growth theory, a representative infinitely-lived household is assumed. As fluctuations in employment are central to the business cycle, the stand-in consumer values not only consumption but also leisure. One very important modification to the standard growth model is that multiple periods are required to build new capital goods and only finished capital goods are part of the productive capital stock. Each stage of production requires a period and utilizes resources. Half-finished ships and factories are not part of the productive capital stock. Section 2 contains a short critique of the commonly used investment technologies, and presents evidence that single-period production, even with adjustment costs, is inadequate. The preference-technology-information structure of the model is presented in Section 3. A crucial feature of preferences is the non-time-separable utility function that admits greater intertemporal substitution of leisure. The exogenous stochastic components in the model are shocks to technology and imperfect indicators of productivity. The two technology shocks differ in their persistence.
The steady state for the model is determined in Section 4, and quadratic approximations are made which result in an “indirect” quadratic utility function that values leisure, the capital goods, and the negative of investments. Most of
1 The research was supported by the National Science Foundation. We are grateful to Scan Becketti, Fischer Black, Robert S. Chirinko, Mark Gersovitz, Christopher A. Sims, and John B. Taylor for helpful comments, to Sumru Altug for research assistance, and to the participants in the seminars at the several universities at which earlier drafts were presented.