Estimating market demand for fresh yam characteristics using contingent valuation: implications for crop breeding and production choices

This study uses the Box-Cox (BC) transformations to examine nonlinearity in price modeling and compare results from several functional specifications in hedonic price analysis of yam in Togo. Based on a sample of 6,402 observations on price and produce characteristics generated through a market experiment, it is found that the BC quadratic asymmetric specification is the most suitable function. Several characteristics are valued more than others, and prices vary across species, time, and market sites. Some residual symptoms of pest and disease damages on yam tubers reduce their market values. Tuber weight exhibits a diminishing marginal value and price per kilogram decreases above an optimum size; therefore, producers do not derive additional reward from extra-large tubers. We conclude that, to effectively access and benefit from urban markets, producers should focus on small size, low weight, and conical shaped-tubers, which are easy to process and meet the esthetic qualities preferred by urban consumers. The implications for research on improved variety development to reduce poverty and for crop and resource management practices are drawn.