Even if there is an agreed-upon, fixed social objective function and policymakers know the timing and magnitude of the effects of their actions, discretionary policy, namely, the selection of that decision which is best, given the current situation and a correct evaluation of the end-of-period position, does not result in the social objective function being maximized. The reason for this apparent paradox is that economic planning is not a game against nature but, rather, a game against rational economic agents. We conclude that there is no way control theory can be made applicable to economic planning when expectations are rational.

Even if there is an agreed-upon, fixed social objective function and policymakers know the timing and magnitude of the effects of their actions, discretionary policy, namely, the selection of that decision which is best, given the current situation and a correct evaluation of the end-of-period position, does not result in the social objective function being maximized. The reason for this apparent paradox is that economic planning is not a game against nature but, rather, a game against rational economic agents. We conclude that there is no way control theory can be made applicable to economic planning when expectations are rational.

An innovation in this paper is to introduce a time‐to‐build technology for the production of market capital into a model with home production. Our main finding is that the two anomalies that have plagued all household production models—the positive correlation between business and household investment, and household investment's leading business investment over the business cycle—are resolved when time to build is added.

The authors ask whether a two-country business cycle model can account simultaneously for domestic and international aspects of business cycles. With this question in mind, the authors document a number of discrepancies between theory and data. The most striking discrepancy concerns the correlations of consumption and output across countries. In this data, outputs are generally more highly correlated across countries than consumptions. In the model they see the opposite.