Estimation of Optimal Commodity Tax Rates in Iran

This study estimates optimal commodity tax rates regarding efficiency and social justice. A many- person Ramsey rule and Bergson – Samuelson social welfare function are used for estimating optimal tax rates. We need to estimate price elasticities of commodities before computing optimal tax rates. These elasticites come from estimation of Almost Ideal Demand System based on household expenditure data, in urban area,s over the period of 1993-2005 and 10 cost deciles. The Almost Ideal Demand System has been estimated by using Panel Data approach. The contrast between efficiency and equity is examined by including a parameter called ''Rate of inequality aversion parameter'' in social welfare function. Optimal tax rates are computed from Lagrange – approach solution of nonlinear systems under alternative assumptions about rate of inequality aversion parameter and fixed Tax Revenues. The Results show that when inequality aversion parameter equals zero, optimal tax of different commodities will be equal. Otherwise, they are different. The larger the parameter, the greater the difference. Tax rates on commodities which have large share in expenditure of lower deciles decrease while tax rates on other commodities increase. Also, with increase of the parameter, marginal cost of the social welfare decreases.