Poverty Traps and Business Cycles in a Stochastic Overlapping Generations Economy with S-shaped Law of Motion.

This paper contributes to the understanding of stochastic economic dynamics with S-shaped law of motion. Applying random dynamical systems theory, we obtain a complete analysis of a stochastic OLG growth model. In the long-run the economy converges either to a state with no capital (poverty trap) or a sample path of a random fixed point (business cycle). The threshold capital stock separating both regimes is a random variable that depends on the future realization of the shocks; this critical level cannot be identified using past observations. Supply of outside capital therefore has an uncertain effect. Policy recommendations are given which cannot be obtained employing Markov equilibria. A numerical illustration is provided.S-shaped stochastic law of motion; random dynamical systems; poverty traps; business cycles; production shocks

Evolutionary Stability of Portfolio Rules in Incomplete Markets

This paper studies the evolution of market shares of portfolio rules in incomplete markets with short-lived assets. Prices are determined endogenously. The performance of a portfolio rule in the process of continuous reinvestment of wealth is determined by the market share eventually conquered in competition with other portfolio rules. Using random dynamical systems theory, we derive necessary and sufficient conditions for the evolutionary stability of portfolio rules. In the case of Markov (in particular i.i.d.) payoffs these local stability conditions lead to a simple portfolio rule that is the unique evolutionary stable strategy. This rule possesses an explicit representation. Moreover, it is demonstrated that mean-variance optimization is not evolutionary stable while the CAPM-rule always imitates the best portfolio rule and survives.evolutionary finance; portfolio theory; market selection; incomplete markets

Volatility-induced Growth in Financial Markets.

We show that the volatility of prices, which is usually regarded as an impediment for financial growth, may serve as a cause of it.

Economic Growth and Business Cycles: A Critical Comment on Detrending Time Series

In this paper we pursue an approach based on economic theory to illustrate possible shortcomings of widely used detrending methods. We analyze a simple model of economic growth and business cycles in which investment and technical progress are stochastic. The Hodrick-Prescott and the Baxter-King filter are shown to detect spurious business cycles that are not related to actual cycles in the model. Our results cast doubts on the validity of commonly accepted stylized business cycle facts. We also discuss the relation of business cycle dating based on indicators of economic activity, as applied, for example, by the National Bureau of Economic Research, and the detrending result

Sample-Path Stability of Non-Stationary Dynamic Economic Systems (Revised Version)

The goal of this paper is to introduce and illustrate a new approach to the stability analysis of sample-paths of nonlinear stochastic economic models with non-stationary components. We place our study within the mathematical theory of random dynamical systems and apply the concept of a random fixed point which is tailor-made for the study of the long-term behavior of sample-paths in stochastic systems. The main tool for the application of this approach is a Banach-type fixed point theorem for non-stationary random dynamical systems which is proved here. The concept and the theorem are thoroughly explained and illustrated by two examples from stochastic growth theory

Survival of the Fittest on Wall Street

This paper studies an application of a Darwinian theory of portfolio selection to stocks listed in the Dow Jones Industrial Average (DJIA). We analyze numerically the long-run outcome of the competition of fix-mix portfolio rules in a stock market with actual DJIA dividends. In the model seemingly rational strategies can do very poorly against seemingly irrational strategies. Moreover, the interaction of strategies can lead to stochastic time series of asset prices that do not converge. The simulations also show that the evolutionary portfolio rule discovered in Hens and Schenk-Hopp´e (2004) will eventually hold total market wealth in competition with fix-mix portfolio rules derived from mean-variance optimization, maximum growth theory and behavioral finance. According to this evolutionary rule, portfolio weights should be proportional to the expected relative dividends of the assets. As an implication asset prices converge to expected relative dividends.Evolutionary Finance; Behavioral Finance; CAPM; Fix-Mix Portfolio Rules; Growth Optimal Portfolio

Markets Do Not Select For a Liquidity Preference as Behavior Towards Risk

Tobin (1958) has argued that in the face of potential capital losses on bonds it is reasonable to hold cash as a means to transfer wealth over time. It is shown that this assertion cannot be sustained taking into account the evolution of wealth of cash holders versus non cash holders. Cash holders will be driven out of the market in the long run by traders who only use a (risky) long-lived asset to transfer wealth.demand for money; portfolio theory; evolutionary finance

(Un)anticipated Technological Change in an Endogenous Growth Model

This paper examines numerically the impact of a negative exogenous shock to marginal productivity (such as ecological government regulation that becomes effective at some point in time) in an endogenous finite-time growth model with sluggish reallocation of human capital. The policy can be anticipated or unanticipated by firms, and it can also be announced but not implemented. It turns out that these frictions have a very strong long-run effect on output, consumption and on the optimal allocation of capital and labor in particular. The qualitative properties relate to homogenous labor models with positive productivity shocks. The problem is thus to maximize a function of a continuous system, where the system is subject to frictions and stepwise changes; for such a problem the application of calculus of variations necessary conditions is problematic. A numerical optimization method, which has had much success on qualitatively similar problems in engineering, has been employed.two-sector endogenous growth model; unanticipated and anticipated technological change; frictions in reallocation of human capital; Runge-Kutta parallel shooting algorithm

On the Micro-foundations of Money: The Capitol Hill Baby-Sitting Co-op.

This paper contributes to the micro-foundation of money in centralized markets with idiosyncratic uncertainty. It shows existence of stationary monetary equilibria and ensures that there is an optimum quantity of money. The rational solution of our model is compared with actual behavior in a laboratory experiment. The experiment gives support to the theoretical approach.micro foundations of money; optimal quantity of money