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.     

Principles for a European Union''s Public Debt

The EU has neither the power to tax nor the right to run a public debt. We analyze if the EU should receive the right for public indebtedness. We make use of the normative theory of public indebtedness and of positive political economy analysis. Our normative analysis identified specific cases for an appropriate use of public indebtedness. According to the political economy analysis, a misuse of public debt may be possible. As the implementation of strict constitutional constraints can limit this misuse, we propose the assignment of a right to public borrowing to the EU within tight constitutional restrictions.     

Should the Good and the Selfish be Taxed Differently?*

In this paper, we consider an environment where individual actions have externalities and two types of agents exist: agents with social preferences (the good) and selfish agents. Selfish agents have pay‐off functions that do not take into account social welfare. The pay‐off of an agent is a linear combination of social welfare and the pay‐off of a selfish agent. We demonstrate that the corrective tax rates that maximize social welfare do not depend on the degree of social preferences. Hence, the good and the selfish should not be taxed differently.     

Real-life cost of vitamin K antagonist treatment in patients with non-valvular atrial fibrillation in France in 2013

Aims: Data highlighting the cost drivers for non-valvular atrial fibrillation (NVAF) patients in terms of vitamin K antagonist (VKA) treatment and monitoring are lacking in France. This study aimed to evaluate the real-life daily cost of VKA treatment in 2013, in French patients suffering from NVAF.

Methods: This longitudinal observational study was performed using the EGB (Echantillon Généraliste des Bénéficiaires) database, a random sample of the French national insurance (NHI) database, which covers 80% of the population. All adult patients whose first NVAF anticoagulant treatment in 2013 was a VKA were analyzed. Costs were calculated for the duration of follow-up and then divided by the number of days of therapy. The analysis was performed both from the French NHI perspective (amount reimbursed by the NHI) and from a collective perspective.

Results: In this study, 3,254 NVAF patients treated with VKA in 2013 were included, and this sample comprised 52.6% males. The mean daily cost of VKA treatment was €1.13 (±1.18) according to the collective perspective (89.4% of this cost was associated to INR measurement) and €1.05 (±1.16) according to the NHI perspective.

Limitations: As diagnoses associated with procedures are not available in the EGB database, proxies were used, and an algorithm was created to define the AF population.

Conclusions: This analysis is the first to consider an exhaustive spectrum of the costs of VKA treatment in France using EGB data. VKA medication requires exhaustive follow-up, and, thus, associated costs are important. The results of the present study confirmed this close follow-up for VKA patients, making the cost of treatment by VKA nearly 10-times more expensive than the cost of medication itself.     

Operational Research and the environment

The discipline of Operational Research (OR) is primarily concerned with improving the effectiveness and efficiency of decision processes. These processes take place everywhere in society: industry, banking, agriculture, government, politics. Frequent use of mathematical optimization models is typical of OR. Since the early '80s these models are increasingly packaged in a user-friendly way, as Decision Support Systems. In the following we will illustrate how OR can be used to describe and solve a number of environmental problems.