Industry dynamics: Foundations for models with an infinite number of firms

This paper explores the connection between three important threads of economic research offering different approaches to studying the dynamics of an industry with heterogeneous firms. Finite models of the form pioneered by Ericson and Pakes (1995) capture the dynamics of a finite number of heterogeneous firms as they compete in an industry, and are typically analyzed using the concept of Markov perfect equilibrium (MPE). Infinite models of the form pioneered by Hopenhayn (1992), on the other hand, consider an infinite number of infinitesimal firms, and are typically analyzed using the concept of stationary equilibrium (SE). A third approach uses oblivious equilibrium (OE), which maintains the simplifying benefits of an infinite model but within the more realistic setting of a finite model. The paper relates these three approaches. The main result of the paper provides conditions under which SE of infinite models approximate MPE of finite models arbitrarily well in asymptotically large markets. Our conditions require that the distribution of firm states in SE obeys a certain “light-tail” condition. In a second set of results, we show that the set of OE of a finite model approaches the set of SE of the infinite model in large markets under a similar light-tail condition.     

VORACIOUS TRANSFORMATION OF A COMMON NATURAL RESOURCE INTO PRODUCTIVE CAPITAL*

I analyze a power struggle where competing factions have private financial assets and deplete a common stock of natural resources with no private property rights. I obtain a feedback Nash equilibrium to the dynamic common‐pool problem and obtain political variants of the Hotelling depletion rule and the Hartwick saving rule. Resource prices and depletion occur too fast, so substitution away from resources to capital occurs too fast and the saving rate is too high. The power struggle boosts output, but depresses sustainable consumption. Genuine saving is nevertheless zero in a fractionalized society. World Bank estimates may be too optimistic.     

The Prosecution of Public Figures and the Separation of Powers. Confusion within the Executive Branch – A Conceptual Framework

Criminal investigation and prosecution of politicians, top civil servants and other public figures are topics frequently discussed in the media. The nature of the investigating or prosecuting authority varies between countries – from the general public prosecutor, through magistrates to independent counsels or parliamentary investigation commissions. This paper analyzes the role and status of public prosecutors within the separation of powers-concept. Prosecutors are usually part of the executive and not the judicial branch, which implies that they do not enjoy the same degree of independence as judges, and are ultimately subordinated to the directives of the minister of justice or the government. Conflicts of interest may hence arise if members of government can use the criminal process for their own or partisan interests. The incentives of public prosecutors in different jurisdictions are compared.     

The impact of rural roads and irrigation on household welfare: evidence from Vietnam

We measure the impact of road and irrigation projects on the livelihoods of households in the poorest and most remote areas of Vietnam using difference-in-difference estimators. We find that both rural road and irrigation projects help local households improve the access to safe water and welfare measured by a wealth index. The impact of irrigation projects is found to be larger than the impact of road projects. We also find heterogeneous impacts of road and irrigation projects. Households with higher levels of education tend to benefit more from road projects, while households with lower levels of education are likely to benefit more from irrigation projects.     

A new proof of the maximum principle

Summary. We offer a new proof of the maximum principle, by using the envelope theorem that is frequently used in the standard microeconomic theory. Received: April 11, 2002; revised version: June 26, 2002 Correspondence to: K. Shimomura     

Existence of a competitive equilibrium in a one sector growth model with heterogeneous agents and irreversible investment

Summary. We prove existence of a competitive equilibrium in a version of a Ramsey (one sector) model in which agents are heterogeneous and gross investment is constrained to be non negative. We do so by converting the infinite-dimensional fixed point problem stated in terms of prices and commodities into a finite-dimensional Negishi problem involving individual weights in a social value function. This method allows us to obtain detailed results concerning the properties of competitive equilibria. Because of the simplicity of the techniques utilized our approach is amenable to be adapted by practitioners in analogous problems often studied in macroeconomics. Received: September 13, 2001; revised version: December 9, 2002 RID="*" ID="*" We are grateful to Tapan Mitra for pointing out errors as well as making very valuable suggestions. Thanks are due to Raouf Boucekkine and Jorge Duran for additional helpful discussions. We also thank an anonymous referee for his/her helpful comments. The second author acknowledges the financial support of the Belgian Ministry of Scientific Research (Grant ARC 99/04-235 “Growth and incentive design”) and of the Belgian Federal Goverment (Grant PAI P5/10, “Equilibrium theory and optimization for public policy and industry regulation”). Correspondence to: C. Le Van     

A live experiment on approval voting

This paper presents a large-scale experiment on the Approval Voting rule that took place during the 2002 French presidential election. We describe the experiment and its main results. The findings are as follows: (i) Such an experiment is feasible, and very well accepted by voters. (ii) The principle of approval voting is easily understood and accepted. (iii) Within the observed political context, compared to the official first-round vote, approval voting modifies the overall ranking of candidates. (iv) The candidates Le Pen and Chirac, more than the others, were able to convert approval votes into official first-round votes. JEL Classification C93, D70, D72     

On the unique features of post-disaster humanitarian logistics

Logistic activity can be thought of as a socio-technical process whereby a social network of individuals orchestrates a series of technical activities using supporting systems such as transportation and communications. To understand the functioning of the entire system requires proper consideration of all its components. We identify seven key components: the objectives being pursued, the origin of the commodity flows to be transported, knowledge of demand, the decision-making structure, periodicity and volume of logistic activities, and the state of the social networks and supporting systems. Based on our analysis of the differences between commercial and humanitarian logistics, we pinpoint research gaps that need to be filled to enhance both the efficiency of humanitarian logistics and the realism of the mathematical models designed to support it.We argue that humanitarian logistics is too broad a field to fit neatly into a single definition of operational conditions. At one end of the spectrum we find humanitarian logistic efforts of the kind conducted in long-term disaster recovery and humanitarian assistance, where operational efficiency – akin to commercial logistics – is a prime consideration. At the other, post-disaster humanitarian logistic operations involved in disaster response and short-term recovery activities represent a vastly different operational environment, often in chaotic settings where urgent needs, life-or-death decisions and scarce resources are the norm. The huge contrast between these operational environments requires that they be treated separately.