Jui-Chen Yang

Taking stock of agroforestry adoption studies

In light of the large number of empirical studies of agroforestry adoption published during the last decade, we believe it is time to take stock and identify general determinants of agroforestry adoption. In reviewing 120 articles on adoption of agricultural and forestry technology by small holders, we find five categories of factors that explain technology adoption within an economic framework: preferences, resource endowments, market incentives, biophysical factors, and risk and uncertainty. By selecting only empirical analyses that focus on agroforestry and related investments, we narrow our list down to 32 studies primarily from tropical areas. We apply vote-counting based meta-analysis to these studies and evaluate the inclusion and significance of the five adoption factors. Our analysis shows that preferences and resource endowments are the factors most often included in studies. However, adoption behavior is most likely to be significantly influenced by risk, biophysical, and resource factors. In our conclusion, we discuss specific recommendations for the next generation of adoption studies and meta-analyses that include considering a fuller menu of variables, reporting key statistics and marginal probabilities, and conducting weighted meta-regressions.

Econometric studies of non-industrial private forest management: a review and synthesis

Abstract Forest policies and management increasingly rely on economic models to explain behaviors of landowners and to project forest outputs, inventories and land use. However, it is unclear whether the existing econometric models offer general conclusions concerning non-industrial private forest (NIPF) management or whether the existing results are case-specific. In this paper, we systematically review the empirical economics literature on NIPF timber harvesting, reforestation, and timber stand improvements (TSI). We confirm four primary categories of management determinants: market drivers, policy variables, owner characteristics and plot/resource conditions. We rely on the most basic form of meta-analysis, vote counting, to combine information from many studies to produce more general knowledge concerning the key determinants of harvesting, reforestation and TSI within these four categories. Despite substantial differences in the variables used across models, the use of meta-analysis enables the systematic identification of the factors that are most important in explaining NIPF management. We conclude with some methodological and policy suggestions.

Household demand for improved piped water services: Evidence from Kathmandu, Nepal

Abstract We examine households’ demand for improved water services in Kathmandu, Nepal, where the government is considering the possibility of involving the private sector in the operation of municipal water supply services. We surveyed a randomly selected sample of 1500 households in the Kathmandu Valley and asked respondents questions in in-person interviews about how they would vote if given the choice between their existing water supply situation and an improved water service provided by a private operator. The results provide the first evidence from South Asia that households’ willingness to pay for improved water services is much higher than their current water bills. We find substantial public support among both poor and nonpoor households for a privatization plan that would improve water supply and require all participants to pay regular and higher monthly bills.

The use of willingness to pay experiments: estimating demand for piped water connections in Sri Lanka

The authors show how willingness to pay surveys can be used to gauge household demand for improved network water and sanitation services. They do this by presenting a case-study from Sri Lanka, where they surveyed approximately 1,800 households in 2003. Using multivariate regression, they show that a complex combination of factors drives demand for service improvements. While poverty and costs are found to be key determinants of demand, the authors also find that location, self-provision, and perceptions matter as well, and that subsets of these factors matter differently for subsamples of the population. To evaluate the policy implications of the demand analysis, they use the model to estimate uptake rates of improved service under various scenarios-demand in subgroups, the institutional decision to rely on private sector provision, and various financial incentives targeted to the poor. The simulations show that in this particular environment in Sri Lanka, demand for piped water services is low, and that it is unlikely that under the present circumstances the goal of nearly universal piped water coverage is going to be achieved. Policy instruments, such as subsidization of connection fees, could be used to increase demand for piped water, but it is unclear whether the benefits of the use of such policies would outweigh the costs.

Effect of pill burden on dosing preferences, willingness to pay, and likely adherence among patients with type 2 diabetes

Purpose To quantify willingness-to-pay (WTP) for reducing pill burden and dosing frequency among patients with type 2 diabetes mellitus (T2DM), and to examine the effect of dosing frequency and pill burden on likely medication adherence. Patients and methods Participants were US adults with T2DM on oral antihyperglycemic therapy. Each patient completed an online discrete-choice experiment (DCE) with eight choice questions, each including a pair of hypothetical medication profiles. Each profile was defined by reduction in average glucose (AG), daily dosing, chance of mild-to-moderate stomach problems, frequency of hypoglycemia, weight change, incremental risk of congestive heart failure (CHF), and cost. Patients were asked to rate their likely adherence to the profiles presented in each question. Choice questions were based on a predetermined experimental design. Choice data were analyzed using random-parameters logit. Likely treatment adherence was analyzed using a Heckman two-stage model. Results Of the 1,114 patients who completed the survey, 90 had lower dosing burden (<5 pills/day taken once/day or as needed) for all medications, and 1,024 had higher dosing burden (≥5 pills/day or more than once/day). Reduction in AG was valued most highly by patients. Hypoglycemia, chance of mild-to-moderate stomach problems, weight change, incremental risk of CHF, and daily dosing were less valued. Patients with higher current dosing burden had lower WTP for more convenient dosing schedules than patients with lower current dosing burden. Changes in dosing and cost impacted likely adherence. The magnitude of the impact of dosing on likely adherence was higher for patients with lower current dosing burden than for patients with higher current dosing burden. Conclusion Patients with T2DM were willing to pay for improvements in efficacy, side effects, and dosing. Patients’ WTP for more convenient dosing depended on current dosing burden, as did the effect of these attributes on likely adherence.

Preferences for public lands management under competing uses: the case of Yellowstone National Park.

We examine snowmobile use conflict in Yellowstone National Park to assess the effect of different winter management policies on heterogeneous visitors’ welfare. Using a stated preference choice experiment we quantify welfare changes for snowmobile riders and non-riders under different snowmobile restrictions. A key determinant of welfare change is visitors’ willingness to trade-off reduced snowmobile access for improved ambient conditions in the park. Our findings support the notion that welfare losses to snowmobile riders could be offset by welfare gains to non-riders, but net benefits will depend on the number of riders and non-riders and the specifics of the policy. (JEL Q26, Q51)

Unpackaging demand for water service quality: evidence from conjoint surveys in Sri Lanka

In the early 2000s, the Government of Sri Lanka considered engaging private sector operators to manage water and sewerage services in two separate service areas: one in the town of Negombo (north of Colombo), and one stretching along the coastal strip (south from Colombo) from the towns of Kalutara to Galle. Since then, the government has abandoned the idea of setting up a public-private partnership in these two areas. This paper is part of a series of investigations to determine how these pilot private sector transactions (forming part of the overall water sector reform strategy) could be designed in such a manner that they would benefit the poor. The authors describe the results of a conjoint survey evaluating the factors that drive customer demand for alternative water supply and sanitation services in Sri Lanka. They show how conjoint surveys can be used to unpackage household demand for attributes of urban services and improve the design of infrastructure policies. They present conjoint surveys as a tool for field experiments and a source of valuable empirical data. In the study of three coastal towns in southwestern Sri Lanka the conjoint survey allows the authors to compare household preferences for four water supply attributes-price, quantity, safety, and reliability. They examine subpopulations of different income levels to determine if demand is heterogeneous. The case study suggests that households care about service quality (not just price). In general, the authors find that households have diverse preferences in terms of quantity, safety, and service options, but not with regard to hours of supply. In particular, they find that the poor have lower ability to trade off income for services, a finding that has significant equity implications in terms of allocating scarce public services and achieving universal water access.

Caregiver Preferences for the Treatment of Males with Fragile X Syndrome.

Objective: Fragile X syndrome (FXS) is the most common inherited form of intellectual disability. The objective of this study was to determine the relative importance that caregivers place on improving different phenotypic traits observed in males with FXS to better understand the greatest medical needs for developing and evaluating FXS treatments. Method: Fragile X syndrome caregivers (n = 614) compared hypothetical treatments in a discrete-choice experiment. The treatments varied in their effects on 6 outcomes associated with FXS: learning and applying new skills, explaining needs, controlling behavior, taking part in new social activities, caring for oneself, and paying attention. The relative importance was calculated for improving severe or moderate levels of disability and transformed to a 10-point scale. Relative importance was also quantified by patient age group (child, adolescent, and adult). Results: Most important to caregivers were controlling behavior (10.0) and caring for oneself (9.9). Least important was taking part in new social activities (4.2). A partial improvement in controlling behavior or self-care was more important than full resolution of the least important disabilities. This was consistent across age groups. Improvements from severe to moderate disability were more important than from moderate to no disability. Conclusion: Caregivers expressed strong preferences for improvement in self-care and behavioral control, independent of the age of the individual with FXS. These data may be helpful when designing studies to test the efficacy of FXS treatments because small treatment effects on very important outcomes may be valued more than large treatment effects on less valued outcomes.

Psoriasis patients’ willingness to accept side-effect risks for improved treatment efficacy

Abstract Background: Previous studies suggest that efficacy is more important than side-effect risks to psoriasis patients. However, those studies did not consider potentially fatal risks of biologic treatments. Objective: To quantify the risks patients are willing to accept for improvements in psoriasis symptoms. Methods: Adults with a self-reported physician diagnosis of psoriasis were recruited through the National Psoriasis Foundation. Using a discrete-choice experiment, patients completed a series of nine choice questions, each including a pair of hypothetical treatments. Treatments were defined by severity of plaques, body surface area (BSA), and 10-year risks of tuberculosis, serious infection and lymphoma. Results: For complete clearance of 25% BSA with mild plaques, respondents (n = 1608) were willing to accept a 20% (95% confidence interval: 9–26%) risk of serious infection, 10% (5–15%) risk of tuberculosis and 2% (1–3%) risk of lymphoma. For complete clearance of 25% BSA with severe plaques, respondents were willing to accept a 54% (48–62%) risk of serious infection, 36% (28–49%) risk of tuberculosis and 8% (7–9%) risk of lymphoma. Limitations: Respondents were asked to evaluate hypothetical scenarios. Actual treatment choices may differ. Conclusion: Respondents were willing to accept risks above likely clinical exposures for improvements in psoriasis symptoms. Individual risk tolerances may vary.

Of taps and toilets: quasi-experimental protocol for evaluating community-demand-driven projects

Sustainable and equitable access to safe water and adequate sanitation are widely acknowledged as vital, yet neglected, development goals. Water supply and sanitation (WSS) policies are justified because of the usual efficiency criteria, but also major equity concerns. Yet, to date there are few scientific impact evaluations showing that WSS policies are effective in delivering social welfare outcomes. This lack of an evaluation culture is partly because WSS policies are characterized by diverse mechanisms, broad goals and the increasing importance of decentralized delivery, and partly because programme administrators are unaware of appropriate methods. We describe a protocol for a quasi-experimental evaluation of a community-demand-driven programme for water and sanitation in rural India, which addresses several evaluation challenges. After briefly reviewing policy and implementation issues in the sector, we describe key features of our protocol, including control group identification, pre-post measurement, programme theory, sample sufficiency and robust indicators. At its core, our protocol proposes to combine propensity score matching and difference-in-difference estimation. We conclude by briefly summarizing how quasi-experimental impact evaluations can address key issues in WSS policy design and when such evaluations are needed.