Estimating inequality in the distribution of welfare using demand models

In this paper two demand models with general household equivalence scales (GES) are estimated. These GES are identifiable, since they have the independence of base utility (IB) or equivalence scales exactness (ESE) property. Estimates of household characteristics adjusted income can then be calculated relative to a specific household type. This “individual equivalent income (IEI) is then used to calculate measures of inequality in the distribution of welfare. As more than one model is estimated, the sensitivity of these estimates to model specification changes can be considered. Comparisons are also made to estimates of inequality based on household income. It is found that absolute inequality is sensitive to model specification, but relative inequality is not. This is true using indices of inequality of the Atkinson (1970), Kolm (1976a,b) and Sen (1973) type, or more general measures of inequality based on estimates of Lorenz curve decile ordinates, constructed using methods introduced by Beach and Davidson (1983). Thus, if absolute measures of inequality are required, these results suggest some further research is required to determine a class of models which is less sensitive to model specification error. However, if only relative measures of inequality are needed, then estimates of inequality appear to be very robust to the choice of model specification.