ABSTRACT

The main objective of this study was to estimate the demand functions and elasticity's for yam (Dioscorea spp) and cocoyam (Xanthosoma spp) in Abia State. Multistage random sampling technique was used in selecting the sample. Ninety (90) yam and seventy (70) cocoyam consuming households were randomly selected from six (6) Local Government Areas. Ordinary Least Squares Multiple Regression technique was used for estimating four demand models which included — Linear, Semi-Log, Exponential, and Double-Log. Linear functional form was used to compare demand for yam with demand for cocoyam, a close substitute in the State. The results revealed that the demand for yam and cocoyam was determined by their own prices, age of household heads and the educational attainment of the household heads. Additional factors influencing the demand for cocoyam but not yam were the price of close substitute and income of the household heads. The estimated price elasticity for yam was — 1.30 and its income elasticity was 0.08. The price elasticity showed anninverse relationship between price and quantity of yam demanded. The positive income elasticity showed yam to be a necessity good since the elasticity value is less than one and positive in the studied area. Similarly, the estimated price elasticity for cocoyam wasl.62 and its income elasticity was -0.08. The price elasticity showed a direct relationship between price and quantity of cocoyam demanded. The positive cross elasticity showed cocoyam to be a close substitute to yam in the studied area. The negative income elasticity showed cocoyam to be an "inferior good". This is a case of abnormal demand. Reducing unit selling prices of yarn can encourage more consumers to demand more yams. Appropriate steps should be taken to make cocoyam available in forms that are readily acceptable to consumers in the study area. The development of appropriate and cost effective farm-level processing technologies is critical for expanding the market for these tuber crops in the future.