Allowing for intra-respondent variations in coefficients estimated on repeated choice data

Partly as a result of the increasing reliance on Stated Choice (SC) data, the vast majority of discrete choice modelling applications are now estimated on data containing multiple observations for each respondent. At the same time there has been growing interest in the representation of unexplained heterogeneity in choice data, using random coefficients models such as Mixed Multinomial Logit (MMNL). The presence of multiple observations for each respondent can indeed be a great asset in the identification of such variations in tastes. However, in this paper, we question the validity of the common assumption that tastes vary across respondents but stay constant across repeated choices for the same respondent. We extend the existing framework for the MMNL analysis of panel data by allowing for intra-respondent heterogeneity on top of inter-respondent heterogeneity. An empirical analysis making use of a SC dataset for route choice confirms our hypotheses and shows that superior performance is obtained by our more general model

Economic Evaluation of Organic and Inorganic Resources for Recapitalizing Soil Fertility in Smallholder Maize-based Cropping Systems of Central Kenya

Structural adjustments programs (SAPs) in the last two decades have eliminated all farm-support programs leading to low usage of fertilizers by Kenyan smallholders. One way of addressing this problem is use of organic nutrient resources. This paper examines their cost-effectiveness as capital investments in replenishment of Nitrogen (N), Phosphorus (P), Potassium (K) and soil organic matter (SOM) in smallholder, Maize-based cropping systems. On-farm trials were established in Maragwa and Kirinyaga Districts in 2003/04. Maize was planted in 3 replicates in randomised complete block design (RCBD) using different levels of organic and inorganic fertilizer resources. A blanket rate of 40kg P/ha was applied in all treatment except the control to increase organic N-utilization efficiency. The test crop was harvested, oven-dried and weighed. Net Present Values (NPV) were computed using Partial Budgeting Analysis Model. Increasing levels of inorganic N increased maize yields significantly (P<0.05). However, higher yields were necessary but not sufficient criteria to determine profitability of different treatments. Manure + 60 kg N/ha gave highest NPV (USD 564), Manure + 40kg N/ha gave second highest NPV (USD 511) in Maragwa District while Manure + 60kg N/ha gave highest NPV (USD 633) and Manure + 40kg N/ha second highest NPV (USD 618) in Kirinyaga District. These results suggested that higher N-levels were not necessarily the most economical. Use of organic resources with modest amounts of mineral fertilizers seemed more profitable and held the key to enhancement of nutrient budgets, food security and rural livelihoods.Natural resource capital, Net present values (NPV), Nutrient budgets, Smallholder farmers, Soil organic matter (SOM), Structural adjustment programs (SAPs), Crop Production/Industries, Land Economics/Use,

Cost-reflective pricing: empirical insights into irrigators’ preferences for water tariffs

© 2017 The Authors. The Australian Journal of Agricultural and Resource Economics published by John Wiley & Sons Australia, Ltd on behalf of Australasian Agricultural and Resource Economics Society Inc. Using prices to improve the efficiency with which water resources are allocated is now widely accepted in principle if somewhat difficult to achieve in practice. Whilst there are some technical difficulties associated with full-cost recovery in irrigation, the lack of political will to tackle reform remains a significant impediment. This article reports the results of an empirical investigation into farmers’ preferences for changes to water prices and tariff structures. We conclude that some of the preferences of farmers are conducive to price reform. We also find evidence that public subsidy of infrastructure in irrigation is not always aligned with the preferences of farmers

Are there specific design elements of choice experiments and types of people that influence choice response certainty?

The development of more realistic choice experiments has taken on board a number of suggestions in the broader hypothetical bias literature. One issue, in particular, is the increasing interest in finding ways to bridge the gap between the stated choice response and real choosing, as a way of increasing the confidence with which an individual would hypothetically purchase or use an alternative that is actually chosen in the choice experiment. In this paper we investigate the relationship between the respondent's response to a certainty question, defined on a 1-10 scale of surety, and features of the choice experiment that may have a bearing on the degree of confidence that can be placed on the stated choice, controlling for exogenous effects such as socioeconomic characteristics and attitudes to vehicle emissions. The focus on response certainty in this paper is as an external validity test. We find, using a generalised ordered logit model, compelling evidence that the number of acceptable alternatives and hence associated levels of attributes, together with the contrast of attribute levels of each designed alternative relative to an experienced status quo (or reference) alternative, play an important role in establishing certainty of response in a real market. The evidence should be taken on board in the future design of more realistic choice experiments

Consumers’ preferences for different energy mixes in Australia

Policy makers worldwide face several challenges in addressing climate change, including an understanding of how to successfully introduce initiatives reliant on renewable energy sources (RES). A key component in this is understanding citizen preferences in terms of willingness to pay (WTP). This research focuses on utilising a discrete choice experiment and associated hybrid choice model to model individual WTP for four different RES types (biomass, hydro, solar and wind) against four current and potential non-RES types (gas, oil, nuclear and coal). The model accounts for latent segments in relation to WTP based on pro-environmental attitudes and various socio-demographics. The research examines the case of Australia, but reports on WTP at each state and territory level rather than at the national level. The findings indicate that respondents from different states and territories have heterogeneous preferences in terms of energy mix composition, which led to different WTP values. A large dissonance emerges also comparing preferences at national and state/territory level, which may potentially act as hindrance to the achievement of the goal set for the Paris agreement

Light attenuation characteristics of glacially-fed lakes

Transparency is a fundamental characteristic of aquatic ecosystems and is highly responsive to changes in climate and land use. The transparency of glacially-fed lakes may be a particularly sensitive sentinel characteristic of these changes. However, little is known about the relative contributions of glacial flour versus other factors affecting light attenuation in these lakes. We sampled 18 glacially-fed lakes in Chile, New Zealand, and the U.S. and Canadian Rocky Mountains to characterize how dissolved absorption, algal biomass (approximated by chlorophyll a), water, and glacial flour contributed to attenuation of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR, 400–700 nm). Variation in attenuation across lakes was related to turbidity, which we used as a proxy for the concentration of glacial flour. Turbidity-specific diffuse attenuation coefficients increased with decreasing wavelength and distance from glaciers. Regional differences in turbidity-specific diffuse attenuation coefficients were observed in short UVR wavelengths (305 and 320 nm) but not at longer UVR wavelengths (380 nm) or PAR. Dissolved absorption coefficients, which are closely correlated with diffuse attenuation coefficients in most non-glacially-fed lakes, represented only about one quarter of diffuse attenuation coefficients in study lakes here, whereas glacial flour contributed about two thirds across UVR and PAR. Understanding the optical characteristics of substances that regulate light attenuation in glacially-fed lakes will help elucidate the signals that these systems provide of broader environmental changes and forecast the effects of climate change on these aquatic ecosystems

Estimating the value of risk reduction for pedestrians in the road environment: An exploratory analysis

In recent years there has been a re-focus on the valuation of a statistical life from the ex post or human capital method to an ex ante willingness to pay (WTP) approach. This is in part a recognition that we need to focus on establishing the amount, ex ante, that individuals are willing to pay to reduce the risk of exposure to circumstances that might lead to death or degree of injury in the road environment. This study sets out a framework in which to identify the degree of preference heterogeneity in WTP of pedestrians to avoid being killed or injured. A stated choice experiment approach is developed. The empirical setting is a choice of walking route for a particular trip that a sample of pedestrians periodically undertakes in Australia. Mixed logit models are estimated to obtain the marginal (dis)utilities associated with each influence on the choice amongst the attribute packages offered in the stated choice scenarios. These conditional estimates are used to obtain the WTP distributions for fatality and classes of injury avoidance, which are then aggregated to obtain estimates for pedestrians of the value of risk reduction (VRR)

Rotation of electromagnetic fields and the nature of optical angular momentum

The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established. The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known. We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges. Crucial to our investigation is the duplex symmetry between the electric and magnetic fields