Capital accumulation games of infinite duration

Consider a market in which firms accumulate capital according to the Nerlove-Arrow capital accumulation equation. Each player chooses a path of investment and thus an induced path of capital to maximize his total discounted profits which depend on his own capital and the capital stocks of his rivals. Existence is proved for such a nonzero sum, infinite horizon differential game and conditions under which the game converges to a particular stationary point, regardless of the initial conditions are shown. Thus, the game possesses the property of conditional global asymptotic stability.     

Output sharing in partnerships as a common pool resource management instrument

Many economic environments are susceptible to either free-riding or overuse. Common pool resources (CPRs) fall in the latter category. Equally sharing the output of a CPR in partnerships introduces a free-riding incentive that may offset overuse. Socially optimal harvesting can be induced by dividing the set of resource users into a number of partnerships in such a way that each resource users’ tendency to over-harvest from the resource is exactly offset by his or her tendency to free-ride on the contributions of others. We conduct a laboratory experiment to assess the performance of this partnership solution by introducing equal-sharing subgroups of size one, four and six into a twelve-person CPR environment. Group assignment is either unchanging throughout a 15 period session or randomly mixed each decision round. Group size significantly affects aggregate effort, while group assignment makes no significant difference. The distribution of total payoffs is more equitable for randomly mixed groups. Implications of our results for voluntary and centralized implementations of the partnership solution are discussed.

A nonsymmetric responding logistic model for forecasting technological substitution

This article presents a simple model of technological substitution termed as nonsymmetric responding logistic (NSRL). Based on the theory that substitution is an imitation process, the model can accommodate different patterns of technological substitution by allowing the imitation effect to vary over time systematically. It allows the S-curve to be symmetrical as well as nonsymmetrical, with the point of inflection responding to the substitution process. Data from four medical innovations are analyzed to illustrate the generality of the model.     

The benefits of being small: Duopolistic competition with market segmentation

Consider a duopolistic market in which consumers are not necessarily aware of the firms' existence. The market is characterized by the existence of four segments: a duopolistic segment which consists of consumers who are aware of both firms, a segment of consumers who are unaware of either firm and two captive market segments. We assume that by advertising, firms control the proportion of consumers who are aware of their existence. The relative sizes of the four segments affect the equilibrium of the duopolistic pricing game. We show that being large may be disadvantageous, and that even if gaining awareness is costless firms may wish to remain small.We would like to thank Paul Klemperer and an anonymous referee for valuable comments.     

Diabetes mellitus--long time survival

The medical literature of the last decade enables us to estimate survival of diabetics. Insulin dependent diabetic (IDDM) present a 3 to 6-fold mortality and die after age 30, the most frequent causes being end stage renal and vascular diseases. Non insulin-dependent diabetic (NIDDM) mortality is 1.4 to 3.7 times that of non-diabetics. Cardiovascular events and strokes are the major causes of death. Pancreatic carcinoma occurs twice as frequently in NIDDM compared to non-diabetics. Early markers of late severe complications are hypertension and proteinuria. Retinopathy has little influence on morality if other risk factors are considered. Yet, glaucoma and lens changes are associated with three- and twofold mortalities. One of five IDDM with microalbuminuria progresses to overt nephropathy in 5 years. In NIDDM micro-albuminuria predicts cardiovascular disease with a mortality of up to 2 times. Careful treatment of cardiovascular risk factors and of microalbuminuria combined with optimal metabolic control substantially reduces mortality of diabetics.     

Comparing econometric methods to empirically evaluate activation programs for job seekers

We test whether different identification strategies give similar results when evaluating activation programs. Budgetary problems at the Dutch unemployment insurance (UI) administration in March 2010 caused a sharp drop in the availability of these programs. Using administrative data provided by the UI administration, we evaluate the effect of the program (1) exploiting the policy discontinuity as a quasi-experiment, (2) using dynamic matching assuming conditional independence, and (3) applying the timing-of-events model. All three strategies use the same data to consider the same program in the same setting, and show that the program reduces job finding directly after enrollment. However, the magnitude of the estimated drop in job finding differs between the three estimation methods. In the longer run, all three methods show a zero effect on employment.