Sharing Some Thoughts on Weitzman's The Share Economy

This paper explores the positive and normative aspects of share contracts. In particular, the paper explores the properties of a share system as advanced by Martin Weitzman in The Share Economy.The model employed highlights a "macroeconomic externality" created in a multi-sector economy with imperfect competition. The introduction of share contracts is shown to influence the comparative static properties of the model economy and in some cases to lead to Pareto superior outcomes.

Dynamic Behavior of Imperfectly Competitive Economies with Multiple Equilibria

This paper investigates the dynamic behavior of an economy with multiple Nash equilibria. The first part of the paper analyzes an abstract game exhibiting multiple equilibria. A history dependent selection criterion is proposed which induces correlated behavior in equilibrium even though agents are playing one-shot games and disturbances are not correlated over time. The second part of the paper investigates a specific model of multiple equilibria. Here the multiplicity is induced by the presence of a discrete decision on the part of firms regarding their choice of technique. The implications of the selection criterion introduced in the first part of the paper are illustrated through this example. Again correlated behavior emerges in a sequence of independent one-shot games. The model economy may also experience prolonged periods in which a low productivity technology is in use and then, as a consequence of a large real disturbance, may switch to an alternative equilibrium in which a high productivity technology is utilized. The paper also discusses the Pareto ordering of these equilibria.

Estimation and Identification of Structural Parameters in the Presence of Multiple Equilibria

This paper studies quantitative implications of model economies that exhibit multiple equilibria. The goal is to assess two interrelated issues. First, do economies with multiple equilibria have falsifiable predictions? Second, is the identification of structural parameters possible in economies that exhibit multiple equilibria? We raise these questions within a general framework and then study a series of examples to determine how the existing literature has addressed them. These examples illustrate cases in which parameters can be identified and models falsified.

Entry and Exit, Product Variety and the Business Cycle

We study the stochastic behavior of a dynamic general equilibrium model with monopolistic competition. Each seller sells his product in the consumption goods as well as the investment goods market and has market power in both. Consumers derive utility from a CES aggregate of all the consumption goods and augment their capital stock by a CES aggregate of all the investment goods. We analyze the equilibrium of this economy allowing for an endogenous determination of the number of firms and therefore of products. The principal effect we highlight is the endogenous propagation and magnification of technology and preference disturbances through product space variations.

Financial Fragility and the Great Depression

We analyze a financial collapse, such as the one which occurred during the Great Depression, from the perspective of a monetary model with multiple equilibria. The economy we consider contains financial fragility due to increasing returns to scale in the intermediation process. Intermediaries provide the link between savers and firms who require working capital for production. Fluctuations in the intermediation process are driven by variations in the confidence agents place in the financial system. Our model matches quite closely the qualitative movements in some financial and real variables (the currency/deposit ratio, ex-post real interest rates, the level of intermediated activity, deflation, employment and production) during the Great Depression period.

Financial Intermediation and The Great Depression: A Multiple Equilibrium Interpretation

This paper explores the behavior of the U.S. economy during the interwar period from the perspective of a model in which the existence of non-convexities in the intermediation process gives rise to a multiplicity of equilibria. The resulting indeterminancy is resolved through a sunspot process which leads to endogenous fluctuations in aggregate economic activity. From this perspective, the Depression period is represented as a regime shift associated with a financial crisis. Our model economy has properties which are broadly consistent with observations over the interwar period. Contrary to observation, the model predicts a negative correlation of consumption and investment as well as a highly volatile capital stock. Our model of financial crisis reproduces many aspects of the Great Depression though the model predicts a much sharper fall in investment than is observed in the data. Modifications to our model (adding durable goods and a capacity utilization choice) do not overcome these deficiencies.

The Dynamics of Car Sales: A Discrete Choice Approach

Mankiw [1982] explores the Permanent Income Hypothesis implication that durable expenditures follow an ARMA(1,1) representation. He finds that durable expenditures are represented by an AR(1) process which implies that the rate of depreciation of durables, under the PIH model, is 100%. This finding presents a puzzle. Our paper builds on earlier work which attempts to explain this puzzle by considering the aggregation of the discrete dynamic choices of heterogeneous households. We implement this approach by estimating a dynamic discrete choice model of car replacement. We find that through aggregation we can explain both the AR and MA components of Mankiw's results. Further we find that our model is able to match a VAR representation of car sales, prices and income. We find that most of the variation in car sales is due to shocks which influence the replacement probability.

Exhuming Q: Market Power vs. Capital Market Imperfections

Evidence of the statistical significance of profits in Q regressions remains one of the principal findings in the empirical investment literature. This result is frequently taken to support the view that capital market imperfections are an important element for understanding investment. This paper challenges that conclusion. We argue that allowing the profit function at the firm level to be strictly concave, reflecting, for example, market power, is sucent to replicate the Q theory based regression results in which profits are a significant factor determining investment. To be clear, our ability to replicate the existing results does not require the specification of any capital market imperfections. Thus the friction that explains the statistical significance of profits could be market power by sellers rather than capital market imperfections.

Deposit Insurance without Commitment: Wall St. versus Main St.

This paper studies the provision of deposit insurance without commitment in an economy with heterogenous households. When households are identical, deposit insurance will be provided ex post to reap insurance gains. But the ex post provision of deposit insurance redistributes consumption when households differ in their claims on the banking system as well as in their tax obligations to finance the deposit insurance. Deposit insurance will not be provided ex post if it requires a (socially) undesirable redistribution of consumption which outweighs insurance gains.