Summary Measures of Equalising Income Mobility Based on Three Is of Mobility Curves
Keywords:
income dynamics, equalising mobility, rerankingAbstract
This article extends the ‘Three Is of Mobility (TIM) Curve’ framework, developed by Creedy and Gemmell (2019) to produce summary measures of equalising mobility between two periods, based on areas within the diagram. Two concepts of equalising mobility are considered. The first involves equalisation of incomes in the second period, achieved by a compression of incomes and no re-ranking. The second concept involves maximum redistribution in terms of the inequality of incomes measured over the two periods combined. This involves differential income growth and maximum re-ranking, whereby second-period incomes are ‘swapped’: the richest person becomes the poorest, and so on. The measures are illustrated using a large sample of taxpayers’ incomes in New Zealand.
References
Creedy, J., and N. Gemmell 2018 “Income dynamics, pro-poor mobility and poverty persistence curves”, Economic Record 94: 316–328. doi.org/10.1111/1475-4932.12426
—– 2019 “Illustrating income mobility: new measures”, Oxford Economic Papers 71(3): 733–755. doi.org/10.1093/oep/gpy057
—– 2022 “Illustrating income mobility and poverty persistence”, Australian Economic Review 55(2): 309–323. doi.org/10.1111/1467-8462.12463
Jenkins, S.P., and P.J. Lambert 1997 “Three ‘I’s of poverty curves, with an analysis of UK poverty trends”, Oxford Economic Papers 49(3): 317–327. doi.org/10.1093/oxfordjournals.oep.a028611
—–, and P. Van Kerm 2016 “Assessing individual income growth”, Economica 83(332): 679–703. doi.org/10.1111/ecca.12205
Van Kerm, P. 2009 “Income mobility profiles”, Economics Letters 102(2): 93–95. doi.org/10.1016/j.econlet.2008.11.022
