Clarke, Ph.

income health index concentration index group grouping inequality concentration correction country gini index distribution correction term value equation number error estimate level income groups income grouping economic measurement category income categories approach indices table iv approach income groupings journal result income rank underestimation function doorslaer difference impact sample measure variable visit figure curve covariance university measurement error individual ourti variance wagstaff weight hospital instrument income inequality information example research observation clarke point point estimate property degree van doorslaer delta study section lorenz curve survey level data weighting function van ourti lorenz concentration indices income distributions panel order monte carlo simulations specialist