ADDITIVE-INTERACTION MODELS OF SPATIAL AGGLOMERATION*

A wide variety of existing models of spatial agglomeration postulate additive-interaction effects among agents. In this paper, a synthesis of such models is achieved by establishing certain mathematical equivalences between them. In particular, it is shown that Rockafellar's conjugacy theory of concave functions yields a symmetric one-to-one correspondence between three classes of existing models, here designated as spatial-accessibility models, endogenous-contact models, and fixed-contact models. These correspondences not only allow the transference of results between models, but also suggest new economic interpretations of each model in terms of its conjugate model. A series of examples are drawn from the literature to illustrate these results.     

Starch granules,dental calculus and new perspectives on ancient diet

Recent work in various parts of the world has suggested the possibility of ancient starch granules surviving and adhering to archaeological artefacts. Often this information is used to infer aspects of diet. One additional source for recovery of archaeological starch granules is dental calculus. The presence of plant food debris in dental calculus is well known but has not been not widely investigated using archaeological material. The extraction of starch granules from dental calculus represents a direct link to the consumption of starchy food by humans or animals. Using dental calculus also sidesteps many other questions still inherent in using starch granules to reconstruct aspects of ancient diet, such as the effects of diagenesis on their morphology; as the starches are trapped inside a concreted matrix they are less likely to alter over time. We used amylase digestion by a starch-specific enzyme to confirm the material as starch.     

TROPICAL DEFORESTATION AND FOREST MANAGEMENT UNDER THE SYSTEM OF CONCESSION LOGGING: A DECISION-THEORETIC ANALYSIS*

ABSTRACT. Deforestation caused by concession logging is often the result of harvest decisions which focus on short-run profits rather than on long-run sustainable harvest yields. A sequential-decision model of this type of behavior is here developed which focuses on a logger's annual decisions of whether or not to remain in compliance with the terms of a concession contract. The contract stipulates harvesting procedures for a sustained forest yield, and noncompliance is taken to result in deforestation. An optimal decision policy for the concession logger is characterized in terms of optimal-stopping theory, and is employed to construct payoff incentives which encourage compliance. In particular, a forest management problem is formulated which focuses on the effectiveness of partial inspection policies in deterring noncompliant behavior. General necessary and sufficient conditions for the effectiveness of such policies are established, and are given a more operational form for the Markov case. A numerical example based on actual concession-contract data is also developed which suggests certain policy implications.     

The distribution of osteoarthritis of the hands in a skeletal population

The distribution of osteoarthritis of the hands was studied in 101 skeletons from archaeological sites in England. The results are similar to those found in epidemiological studies of modern populations. Osteoarthritis of the hands was more common in females than in males, and in females tended to involve a greater number of joints. The distal and proximal interphalangeal joints were commonly affected, the former more frequently than the latter, but otherwise the disease was largely confined to the first ray of the hand, centred on the trapezium. It is concluded that the pattern of osteoarthritis in the hand has probably not changed greatly over several hundred years.     

Institutional Influences on EU Funded Regional Technology Development in the UK: A Study of the Yorkshire and East London Regions in the 1990s

This paper seeks to place policy research undertaken in the Yorkshire and East London regions of the UK within the broader context of regional innovation system building. In particular, it attempts to draw out the releasing factors and conditions that shaped stakeholder relationships in these two EU Objective Two regions during the 1990s. This is undertaken with a view to drawing out conclusions about the extent of autonomy, institutional lock-in and compatibility within regional governance. The extent to which such EU stimulated influences are relevant to the practice of regional technological development is explored in areas which have experienced industrial restructuring.     

Property Rights and the Environment in Pastoral China: Evidence from the Field

It is widely perceived that the degradation of China’s rangelands has accelerated since the introduction of rural reforms in the late 1970s. The popular explanation for this phenomenon has been that a ‘tragedy of the commons’ exists, as privately‐owned livestock are being grazed on ‘common’ land. Since the passing of the Rangeland Law in 1985, Chinese pastoral tenure policy has emphasized the establishment of individual household tenure as a necessary condition for improving incentives for sustainable rangeland management. Yet household tenure has yet to be effectively established in many pastoral regions. The first objective of this article is to describe pastoral tenure arrangements in northern Xinjiang‐Uygur Autonomous Region. Its second objective is to explain pastoral tenure arrangements, particularly the observed persistence of collective action. It is argued that there is no ‘tragedy of the commons’ and that it is characteristics of rangeland resources and the social environment that give rise to the particular types of institutional arrangements found.