Abstracts of award-winning theses.

Smith-Ramirez, Ricardo. "On the Evaluation of Conservation Cost-Sharing Programs. An Application of a Monte Carlo EM Algorithm." Ph.D. Dissertation, University of Maryland. Outstanding Ph.D. Dissertation Award.

This dissertation develops and applies a Monte Carlo Expectation Maximization (EM) algorithm to estimate systems of linear equations with incomplete information by maximum likelihood. Applications are carried out on farm-level data to obtain estimates of the effects of two conservation cost-sharing programs. Cost-sharing programs have three features that complicate econometrics, namely, (1) participation is endogenous; (2) programs are multi-objective, which makes it necessary to consider a number of interrelated response variables in the analysis; and (3) most frequently observed responses involve some type of incomplete information (i.e., responses are discrete, censored, or just unobserved at all). Depending on the nature of the incomplete information, applied literature offers a number of (ad hoc) selectivity and switching regression models to deal with these issues. All the models, however, have a common limitation: they cannot involve a large number of latent variables because intractable high-dimensional integrals show up in the likelihood function. The dissertation shows that all of these models can be treated as special cases of the generalized linear model, which admits a GLS type solution. The algorithm combines a Gibbs sampler in the expectation step to circumvent high-dimensional integrals; sequential maximizations in the maximization step; and a stochastic version of the Louis formula to estimate the information matrix. The first application investigates the impact of conservation cost-sharing programs in Maryland. Results indicate that subsidies for adoption of land quality enhancing practices expand cropping on marginal land, hence reducing permanent vegetative cover. The second application analyzes a soil fertility remediation program in Chile. More specifically, (1) it tests the existence of different optimal paths to recover phosphorus fertility, and (2) it evaluates how a subsidy affects phosphorus stock conditional on the path chosen by the farmer.

"Parental Time and Children's Obesity Measures: A Theoretical and Empirical Investigation." You, Wen, Texas A&M University. Outstanding Ph.D. Dissertation Award.

This study aims to explore the different influence mothers and fathers have on child obesity-related health outcomes. A household with two parents and one child is modeled. The model treats the mother, the father, and the child as three separate agents with individual preferences. The parents' interaction is modeled within the collective household model framework. To capture the dynamics between the parents and the child, the parents-child interaction is modeled as a two-stage Stackleberg game. This game structure allows the parents to influence the child's health outcome separately while allowing the child to have influence in the household decision-making process.

Based on this theoretical model, a general triangular system with one child's health production equation and five health input demand equations is derived and estimated. The empirical estimation is performed for three systems: a pooled model, the younger children model (of age nine to eleven), and the older children model (of age thirteen to fifteen). The empirical results indicate that mother-related variables show more influence on the child's Body Mass Index (BMI) outcomes compared to father-related variables: mothers' BMI and mothers' work-to-home stress spillover are positively related to their children's BMI while mothers' time spent with their children is negatively related to their children's BMI. There exists a complementary relationship between mothers' income and fathers' non-market work time. In the older children model, mothers' own income increases tend to decrease their time spent with their children.

The main contribution of this study is that it develops a general theoretical framework to capture the dynamics in parents-child interaction. Based on this theoretical model, empirical analysis and future work can be conducted in a theoretically consistent way.

Yao, Richard Tolentino. "Impacts of Irrigation Development on Agricultural Productivity, Resource Allocation, and Income Distribution: A Longitudinal Analysis from Palawan, The Philippines." M.S. thesis, Purdue University. Outstanding Master's Thesis Award.

This study evaluates the impacts of irrigation development on farming communities in Palawan, the Philippines focusing on three issues: (1) production efficiency in the lowland communities directly affected by irrigation; (2) activity and asset allocation in the adjacent upland communities indirectly affected by irrigation; and (3) patterns of income inequality and poverty within and between these two groups of communities. To study lowland production efficiency, a stochastic frontier analysis using an error decomposition technique is used on an unbalanced parcel-level data set. To study upland resource allocation, a seemingly unrelated regressions approach is employed. In studying the distributional

Thomas R. Harris is a professor and Director. Department of Resource Economics. University Center for Economic Development University of Nevada.

This article was presented in a principal paper session at the AAEA annual meeting (Long Beach, CA. July 2006). The articles ill these sessions are not subjected to the journal's standard refereeing process.

impact, inequality indices and the Gini decomposition technique are used. To examine irrigation's impact on poverty alleviation, poverty indices and poverty decomposition techniques are used.

Analyses suggest that irrigation has benefited both the lowland farmers and the adjacent upland farming communities. Lowland farmers experienced higher technical efficiency in rice production, improved income distribution, and lower poverty incidence with irrigation development. Results indicate that, through hiring of farm laborers in the lowland farming communities, irrigation serves as a channel through which lowland agricultural development provided important economic, environmental, and distributional benefits in the adjacent uplands.

Overall, results show strong benefits from irrigation development. One unfavorable impact of irrigation development is that it appears to have led to wider income inequality between lowland and upland communities. The lowlands became relatively better off and the uplands became relatively worse off. However, upland households with offfarm work were found to be less worse off in absolute terms and better off in relative terms than those with no off-farm work. (1)

(1) For this study, the term "off-farm work" refers to working on someone else's farm. Upland farmers who had been employed on lowland rice farms were considered to have engaged in off-farm work.