Measurement of inequity in health care with heterogeneous response of use to need.

We propose a method of measuring and decomposing inequity in health care utilisation that allows for heterogeneity in the use-need relationship. This makes explicit inequity that derives from unequal treatment response to variation in need, as well as that due to differential effects of non-need determinants. Under plausible conditions concerning heterogeneity in the use-need relationship and the distribution of need, existing methods that impose homogeneity will underestimate pro-rich inequity. This prediction is confirmed for four middle-income Asian countries. In those countries, around one half of the observed socioeconomic inequality is due to utilisation being more responsive to need among the higher wealth and urban dwelling individuals.