Job Mix, Performance Pay, and Matching Outcomes: Contracting with Multiple Heterogeneous Agents

We examine the problem of designing performance contracts with multiple agents when principals must compete for quality teams from a heterogeneous pool of agents. The trade-off principals face between good recruiting and good team performance provides micro foundations for agents to form stable matches, and for initially identical principals to adopt different organizational schemes. The equilibrium pattern of team formation exhibits two distinct, and inversely related, forms of assortative matching. We find that a greater share of principals offering diverse performance incentives across teammates (extensive margin), leads to a lesser degree of heterogeneity in abilities within teams on average (intensive margin). We apply the model to firm behavior to examine the mix of jobs offered and the degree of performance pay in a general equilibrium environment. At the aggregate level, increases in the supply of high-skilled workers leads to a polarization of jobs offered, i.e. relatively greater use of high- and low- skill occupations, consistent with changing labor demands in recent history. Moreover, skill accumulation among the labor force induces more firms to offer a steep set of performance contracts.Multi-Agent Contracting, Matching, Job Design

How did the location of industry respond to falling transport costs in Britain before World War I?

This article explores the location of industry in pre–World War I Britain using a model that takes account both of factor endowment and also of New Economic Geography influences. Broadly speaking, the pattern of industrial location in this period was quite persistent and regional specialization changed little. The econometric results show that factor endowments had much stronger effects than proximity to markets, although the latter was an attraction for industries with large plant size. Overall, falling transport costs had relatively little effect on industrial location at a time when proximity to natural resources, notably coal, mattered most

Myocardial Architecture and Patient Variability in Clinical Patterns of Atrial Fibrillation

Atrial fibrillation (AF) increases the risk of stroke by a factor of four to five and is the most common abnormal heart rhythm. The progression of AF with age, from short self-terminating episodes to persistence, varies between individuals and is poorly understood. An inability to understand and predict variation in AF progression has resulted in less patient-specific therapy. Likewise, it has been a challenge to relate the microstructural features of heart muscle tissue (myocardial architecture) with the emergent temporal clinical patterns of AF. We use a simple model of activation wavefront propagation on an anisotropic structure, mimicking heart muscle tissue, to show how variation in AF behaviour arises naturally from microstructural differences between individuals. We show that the stochastic nature of progressive transversal uncoupling of muscle strands (e.g., due to fibrosis or gap junctional remodelling), as occurs with age, results in variability in AF episode onset time, frequency, duration, burden and progression between individuals. This is consistent with clinical observations. The uncoupling of muscle strands can cause critical architectural patterns in the myocardium. These critical patterns anchor micro-re-entrant wavefronts and thereby trigger AF. It is the number of local critical patterns of uncoupling as opposed to global uncoupling that determines AF progression. This insight may eventually lead to patient specific therapy when it becomes possible to observe the cellular structure of a patient's heart.Comment: 5 pages, 4 figures. For supplementary materials please contact Kishan A. Manani at [email protected]

Developing site-specific guidelines for orchard soils based on bioaccessibility – Can it be done?

Horticultural land within the periurban fringe of NZ towns and cities increasingly is being developed for residential subdivision. Recent surveys have shown that concentrations of As, Cd, Cu, Pb, and ΣDDT (sum of DDT and its degradation products DDE and DDD) in such soils can exceed criteria protective of human health.¹ Soil ingestion is a key exposure pathway for non-volatile contaminants in soil. Currently in NZ, site-specific risk assessments and the derivation of soil guidelines protective of human health assume that all of the contaminant present in the soil is available for uptake and absorption by the human gastrointestinal tract. This assumption can overestimate health risks and has implications for the remediation of contaminated sites.² In comparison, the bioavailability of contaminants is considered when estimating exposure via dermal absorption and by ingestion of home-grown produce.³ Dermal absorption factors and plant uptake factors are included in the calculations for estimating exposures via these routes

Avalanche Behavior in an Absorbing State Oslo Model

Self-organized criticality can be translated into the language of absorbing state phase transitions. Most models for which this analogy is established have been investigated for their absorbing state characteristics. In this article, we transform the self-organized critical Oslo model into an absorbing state Oslo model and analyze the avalanche behavior. We find that the resulting gap exponent, D, is consistent with its value in the self-organized critical model. For the avalanche size exponent, \tau, an analysis of the effect of the external drive and the boundary conditions is required.Comment: 4 pages, 2 figures, REVTeX 4, submitted to PRE Brief Reports; added reference and some extra information in V