A dynamic almost ideal demand model for US catfish

Abstract

The study applies a dynamic model of the almost ideal demand system to derive long‐run estimates of demand for catfish products. Adjustment coefficients towards long‐run equilibrium for purchasers of catfish are estimated. The hypothesis that catfish buyers fully adjust to changes in real price and expenditure instantaneously is rejected. Following a deviation from equilibrium, about 16% of the adjustment takes place instantaneously while full adjustment is completed within the subsequent two‐month period. Purchasers of catfish adjust fairly quickly to a new equilibrium after disequilibrium movements suggesting a low cost of adjustment. Elasticity estimates obtained from the model indicate that the dynamic model is well behaved, with negative own‐price effects in the compensated and uncompensated form. In the uncompensated form whole fish is found to be less own‐price inelastic while fillet is found to be own‐price elastic. The sensitive nature of the products to changes in own prices suggests the need for processors to make whole fish and fillets more price‐competitive through efficient production and marketing processes. Expenditure elasticities obtained from the model are also consistent with economic theory.