health and, thus, there is some aversion to inequality. If ν = 2 then (2) reduces to (1) and becomes
equal to the standard concentration index. As ν gets larger, the weighting becomes more pro-poor.
If ν =∞then (2) becomes 1 − mini
hi
μ(h) , i.e. all weight goes to the worst-ranked individual.
Wagstaff (2002) went on to propose what he labeled an achievement index, which in the notation
of this paper is defined as