Garth Holloway

Adaptive human behavior in epidemiological models

The science and management of infectious disease are entering a new stage. Increasingly public policy to manage epidemics focuses on motivating people, through social distancing policies, to alter their behavior to reduce contacts and reduce public disease risk. Person-to-person contacts drive human disease dynamics. People value such contacts and are willing to accept some disease risk to gain contact-related benefits. The cost–benefit trade-offs that shape contact behavior, and hence the course of epidemics, are often only implicitly incorporated in epidemiological models. This approach creates difficulty in parsing out the effects of adaptive behavior. We use an epidemiological–economic model of disease dynamics to explicitly model the trade-offs that drive person-to-person contact decisions. Results indicate that including adaptive human behavior significantly changes the predicted course of epidemics and that this inclusion has implications for parameter estimation and interpretation and for the development of social distancing policies. Acknowledging adaptive behavior requires a shift in thinking about epidemiological processes and parameters.

Policy options promoting market participation among smallholder livestock producers: a case study from the Phillipines

We investigate the factors precipitating market entry where smallholders make decisions about participation (a discrete choice about whether to sell quantities of products) and supply (a continuous-valued choice about how much quantity to sell) in a cross-section of smallholders in Northern Luzon, Philippines, in a model that combines basic probit and Tobit ideas, is implemented using Bayesian methods, and generates precise estimates of the inputs required in order to effect entry among the non-participants. We estimate the total amounts of (cattle, buffalo, pig and chicken) livestock input required to effect entry and compare and contrast the alternative input requirements. To the extent that our smallholder sample may be representative of a wide and broader set of circumstances, our findings shed light on offsetting impacts of conflicting factors that complicate the roles for policy in the context of expanding the density of participation.

Demand, Supply and Willingness-to-Pay for Extension Services in an Emerging-Market Setting

Although it may be wholly inappropriate to generalize, the most important resource available to a subsistence household is the total amount of time that its members have available to spend in productive enterprises. In this context, services that minimize the time that it takes to perform productive activities are valuable to the household. Consequently the household is willing to relinquish quantities of other resources in exchange for quantities of the time-saving service. These simple observations motivate a search for the values that subsistence households place on time-saving services. This search is especially important when it is realized that extension services promote productivity, enhance the surplus-generating potential of the household and can, as a consequence, promote immersion into markets that are currently constrained by thinness and instability. In this capacity, extension visitation has the potential to overcome one of the principal impediments to economic development, namely lack of density of market participation. In this article, we consider this issue in the context of a rich data set on milk-market participation by small-holder dairy producers in the Ethiopian highlands.

THE DOUBLE HURDLE MODEL IN THE PRESENCE OF FIXED COSTS

We present a model of market participation in which the presence of nonnegligible fixed costs leads to non-zero censoring of the traditional double-hurdle regression. Fixed costs arise when household resources must be devoted a priori to the decision to participate in the market. These costs - usually a cost of time - motivate two-step decision-making and focus attention on the minimum-efficient scale of operations (the minimum amount of milk sales) at which market entry becomes viable. This focus, in turn, motivates a non-zero-censored Tobit regression estimated through routine application of Markov chain Monte Carlo Methods.

Production Efficiency in the von Liebig Model

The objective of this paper is to revisit the von Liebig hypothesis by reexamining five samples of experimental data and by applying to it recent advances in Bayesian techniques. The samples were published by Hexem and Heady as described in a further section. Prior to outlining the estimation strategy, we discuss the intuition underlying our approach and, briefly, the literature on which it is based. We present an algorithm for the basic von Liebig formulation and demonstrate its application using simulated data (table 1). We then discuss the modifications needed to the basic model that facilitate estimation of a von Liebig frontier and we demonstrate the extended algorithm using simulated data (table 2). We then explore, empirically, the relationships between limiting water and nitrogen in the Hexem and Heady corn samples and compare the results between the two formulations (table 3). Finally, some conclusions and suggestions for further research are offered.

Estimating regional benefits of reducing targeted pollutants: an application to agricultural effects on water quality and the value of recreational fishing

The general focus of this paper is the regional estimation of marginal benefits of targeted water pollution abatement to instream uses. Benefit estimates are derived from actual consumer choices of recreational fishing activities and the implied expenditures for various levels of water quality. The methodology is applied to measuring the benefits accruing to recreational anglers in Indiana from the abatement of pollutants that are by-products of agricultural crop production.

Hierarchical Analysis of Production Efficiency in a Coastal Trawl Fishery

We present, pedagogically, the Bayesian approach to composed error models under alternative, hierarchical characterizations; demonstrate, briefly, the Bayesian approach to model comparison using recent advances in Markov Chain Monte Carlo (MCMC) methods; and illustrate, empirically, the value of these techniques to natural resource economics and coastal fisheries management, in particular. The Bayesian approach to fisheries efficiency analysis is interesting for at least three reasons. First, it is a robust and highly flexible alternative to commonly applied, frequentist procedures, which dominate the literature. Second, the Bayesian approach is extremely simple to implement, requiring only a modest addition to most natural-resource economist tool-kits. Third, despite its attractions, applications of Bayesian methodology in coastal fisheries management are few.

The problem with boys: Bridewealth accumulation, sibling gender, and the propensity to participate in cattle raiding among the Kuria of Tanzania

Although a fair amount has been written on the subject of African “crime” in general (e.g., Read 1964, Brillon 1985, Austen 1986, Cohen 1986, Crummey 1986) and East African livestock theft in particular (e.g., Fukui and Turton 1979, Anderson 1986, Hendrickson, Mearns, and Armon 1996), scant effort has been made to establish who, in a sociological sense, these “criminals” are (but see Moore 1975 and Heald 1986 for two noteworthy exceptions). This article endeavors to contribute to this effort using field data collected among the agro-pastoral Kuria of Tarime District in northern Tanzania. Among the Kuria, whose population straddles the border between Tanzania and Kenya, many young men are actively engaged in an illict livestock trade in which cattle stolen in Tanzania—mainly from other Kuria but also from neighboring peoples—are sold to buyers, mainly butchers, inside Tanzania or else run across the border for cash sale in Kenya. Kuria cattle raiding is by no means a new phenomenon, but it has undergone a profound transformation in the course of the past century—from its precolonial roles of demonstrating the mettle of new warriors and enlarging the community cattle herd to an illict, often quite violent cash-marketoriented enterprise—in response to the pressures exerted by the colonial economy, capitalist penetration, and the policies of the postcolonial Tanzanian state (Fleisher 2000a, b). Fleisher (1999) has already demonstrated that, among the Kuria, cattle theft is overwhelmingly the “occupa-

When Do Export Subsidies Have a Redistributional Role

If an export subsidy is efficient, that is, has a surplus-transfer role, then there exists an implicit function relating the optimal level of the subsidy to the income target in the agricultural sector. If an export subsidy is inefficient no such function exists. We show that dependence exists in large-export equilibrium, not in small-export equilibrium and show that these results remain robust to concerns about domestic tax distortions. The failure of previous work to produce this result stems from its neglect of the income constraint on producer surplus in the programming problem transferring surplus from consumers and taxpayers to farmers. Copyright 2002, Oxford University Press.

Bayesian Estimation of the Spatial Durbin Error Model with an Application to Voter Turnout in the 2004 Presidential Election

The potential for spatial dependence in models of voter turnout, although plausible from a theoretical perspective, has not been adequately addressed in the literature. Using recent advances in Bayesian computation, the authors formulate and estimate the previously unutilized spatial Durbin error model and apply this model to the question of whether spillovers and unobserved spatial dependence in voter turnout matters from an empirical perspective. Formal Bayesian model comparison techniques are employed to compare the normal linear model, the spatially lagged X model (SLX), the spatial Durbin model, and the spatial Durbin error model. The results overwhelmingly support the spatial Durbin error model as the appropriate empirical model.