On durable goods markets with entry and adverse selection

Abstract. We investigate the nature of trading and sorting induced by the dynamic price mechanism in a competitive durable good market with adverse selection and exogenous entry of traders over time. The model is a dynamic version of Akerlof (1970) . Identical cohorts of durable goods, whose quality is known only to potential sellers, enter the market over time. We show that there exists a cyclical equilibrium where all goods are traded within a finite number of periods after entry. Market failure is reflected in the length of waiting time before trade. The model also provides an explanation of market fluctuations. JEL classification: D82 A propos des marchés de biens durables quand il y a entrée de nouveaux commerçants et sélection adverse. Les auteurs analysent la nature du commerce et du triage engendrés par le mécanisme dynamique des prix dans un marché concurrentiel de biens durables quand il y a sélection adverse et entrée exogène de nouveaux commerçants dans le temps. Ce modèle est une version dynamique du modèle d’ Akerlof (1970) . Des cohortes identiques de biens durables, dont la qualité est connue seulement des vendeurs potentiels, arrivent sur le marché dans le temps. Il semble qu’il y ait plus de commerce actif que ce qui est prévu par un modèle statique. En particulier, on montre qu’il existe un équilibre cyclique où tous les biens sont transigés à l’intérieur d’un nombre fini de périodes après leur arrivage et que, à chaque phase du cycle, l’éventail de qualité des biens transigés s’accroît. Les commerçants qui transigent des produits de plus haute qualité attendent plus longtemps et l’imperfection du marché se traduit par la longueur de temps d’attente avant la transaction. Le modèle fournit aussi une explication des fluctuations du marché.     

A landscape approach for assessing the biodiversity value of indigenous forest remnants: Case study of the Manawatu/Wanganui region of New Zealand

To halt the decline of biodiversity in New Zealand, the government has formulated a strategy of maintaining and restoring a full range of remaining natural habitats to a healthy functioning state. Many indigenous forest remnants exist on private land, and these could be utilised to increase biodiversity. Resources for conservation of forest remnants are limited, so they must be used wisely to deliver the greatest possible biodiversity gain. This paper presents a rapid method for valuing the biodiversity of a region's indigenous forest remnants to help prioritise conservation resources. The region is divided into environmentally distinct areas called land environments. A detailed land-cover map is derived from satellite imagery and used to estimate the proportion of natural habitats remaining in each land environment; from this the biodiversity value of any forest remnant may be calculated. The method is rapid and does not require detailed biodiversity information. When combined with conservation costs, it may be used to create a priority list of forest remnants for conservation. The Manawatu/Wanganui region of New Zealand is used as a case study to demonstrate the method.     

The effectiveness of government spending on education and health care in developing and transition economies

Recent studies show that corruption is associated with higher military spending [Eur. J. Polit. Econ. 17 (2001) 794] and lower government spending on education and health care [J. Publ. Econ. 69 (1998) 263]. This suggests that policies aimed at reducing corruption may lead to changes in the composition of government outlays toward more productive spending. However, little empirical evidence has been presented to support the claim that public spending improves education and health indicators in developing and transition countries. This paper uses cross-sectional data for 50 such countries to show that increased public expenditure on education and health care is associated with improvements in both access to and attainment in schools, and reduces mortality rates for infants and children. The education regressions are robust to different specifications, but the relationship between health care spending and mortality rates is weaker.     

Dynamic Insurance Contracts and Adverse Selection

We take a dynamic perspective on insurance markets under adverse selection and study a dynamic version of the Rothschild and Stiglitz model. We investigate the nature of dynamic insurance contracts by considering both conditional and unconditional dynamic contracts. An unconditional dynamic contract has insurance companies offering contracts where the terms of the contract depend on time, but not on the occurrence of past accidents. Conditional dynamic contracts make the actual contract also depend on individual past performance (such as in car insurances). We show that dynamic insurance contracts yield a welfare improvement only if they are conditional on past performance. With conditional contracts, the first‐best can be approximated if the contract lasts long. Moreover, this is true for any fraction of low‐risk agents in the population.     

A randomized trial to assess the effectiveness of an infant home safety programme

The aim of this study was to test an intervention aimed at addressing the risk of injury in infants 2 - 12 months of age. A non-blinded, randomized controlled trial was conducted, whereby parents were randomly assigned to either a control or one of two intervention groups. Parents completed questionnaires regarding safety behaviours and injuries at the 2 (baseline), 6 and 12 month immunization visit at the community health unit. During the 2 month visit to the health unit, the two intervention groups received a home safety kit containing nine items, an instructional brochure and a risk assessment checklist. Subjects randomized to the safety kit plus home visit group also received a standardized home visit from a community health nurse. Two of the 14 parental safety behaviours showed a significant increase in use among parents in the intervention groups. Neither of the interventions was associated with a reduction in parent-reported injuries among children. It was concluded that home visitation may provide a beneficial adjunct to the provision of safety devices and may increase use by parents.     

Will It Spread or Not? The Effects of Social Influences and Network Topology on Innovation Diffusion

Innovation diffusion theory suggests that consumers differ concerning the number of contacts they have and the degree and the direction to which social influences determine their choice to adopt. To test the impacts of these factors on innovation diffusion, in particular the occurrence of hits and flops, a new agent‐based model for innovation diffusion is introduced. This model departs from existing percolation models by using more realistic agents (both individual preferences and social influence) and more realistic networks (scale free with cost constraints). Furthermore, it allows consumers to weight the links they have, and it allows links to be directional. In this way this agent‐based model tests the effect of VIPs who can have a relatively large impact on many consumers. Results indicate that markets with high social influence are more uncertain concerning the final success of the innovation and that it is more difficult for the innovation to take off. As consumers affect each other to adopt or not at the beginning of the diffusion, the new product has more difficulties to reach the critical mass that is necessary for the product to take off. In addition, results of the simulation experiments show under which conditions highly connected agents (VIPs) determine the final diffusion of the innovation. Although hubs are present in almost any network of consumers, their roles and their effects in different markets can be very different. Using a scale‐free network with a cut‐off parameter for the maximum number of connections a hub can have, the simulation results show that when hubs have limits to the maximum number of connections the innovation diffusion is severely hampered, and it becomes much more uncertain. However, it is found that the effect of VIPs on the diffusion curve is often overestimated. In fact when the influence of VIPs on the decision making of the consumers is strengthened compared with the influence of normal friends, the diffusion of the innovation is not substantially facilitated. It can be concluded that the importance of VIPs resides in their capacity to inform many consumers and not in a stronger persuasive power.     

Catching hipos: screening, wages, and competing for a job

In this paper, I study the wage a firm sets to attract highability workers (hipos) in situations where people compete fora job. I show that the more people compete, the larger a firm'sincentives to sort high and low ability workers. Moreover, workerswill signal their (high) ability in situations with many competitorsonly if a job offers a high enough wage. The main result, therefore,is that a firm sets higher wages, when more people compete.     

Local asymptotic normality for randomly censored models with applications to rank tests

For randomly right censored models we study the asymptotic behaviour of linear (rank) statistics under local alternatives. The results can be used to evaluate the asymptotic power of the corresponding tests. For instance we treat the question how to choose the best scores in order to derive asymptotically optimal (rank) tests under certain alternatives.