The Gini coefficient and discontinuity

This article reveals a discontinuity in the mapping from a Lorenz curve to the associated cumulative distribution function. The problem is of a mathematical nature—based on an analysis of the transformation between the distribution function of a bound random variable and its Lorenz curve. It will be...

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Main Author: Jens Peter Kristensen
Format: Article
Language:English
Published: Taylor & Francis Group 2022-12-01
Series:Cogent Economics & Finance
Subjects:
Online Access:https://www.tandfonline.com/doi/10.1080/23322039.2022.2072451
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author Jens Peter Kristensen
author_facet Jens Peter Kristensen
author_sort Jens Peter Kristensen
collection DOAJ
description This article reveals a discontinuity in the mapping from a Lorenz curve to the associated cumulative distribution function. The problem is of a mathematical nature—based on an analysis of the transformation between the distribution function of a bound random variable and its Lorenz curve. It will be proven that the transformation from a normalized income distribution to its Lorenz curve is a continuous bijection with respect to the [Formula: see text] ([0,1])-metric—for every q ≥ 1. The inverse transformation, however, is not continuous for any q ≥ 1. This implies a more careful attitude when interpreting the value of a Gini coefficient. A further problem is that if you have estimated a Lorenz curve from empirical data,then you cannot trust that the associated distribution is a good estimate of the true income distribution.
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spelling doaj-art-e2cf4541bc624f4a9bab6f78cdb4e8142025-08-20T02:16:46ZengTaylor & Francis GroupCogent Economics & Finance2332-20392022-12-0110110.1080/23322039.2022.2072451The Gini coefficient and discontinuityJens Peter Kristensen0Retired lecturer, M. Sc. in mathematics, DenmarkThis article reveals a discontinuity in the mapping from a Lorenz curve to the associated cumulative distribution function. The problem is of a mathematical nature—based on an analysis of the transformation between the distribution function of a bound random variable and its Lorenz curve. It will be proven that the transformation from a normalized income distribution to its Lorenz curve is a continuous bijection with respect to the [Formula: see text] ([0,1])-metric—for every q ≥ 1. The inverse transformation, however, is not continuous for any q ≥ 1. This implies a more careful attitude when interpreting the value of a Gini coefficient. A further problem is that if you have estimated a Lorenz curve from empirical data,then you cannot trust that the associated distribution is a good estimate of the true income distribution.https://www.tandfonline.com/doi/10.1080/23322039.2022.2072451inequalityprobabilitymath analysisdiscontinuity
spellingShingle Jens Peter Kristensen
The Gini coefficient and discontinuity
Cogent Economics & Finance
inequality
probability
math analysis
discontinuity
title The Gini coefficient and discontinuity
title_full The Gini coefficient and discontinuity
title_fullStr The Gini coefficient and discontinuity
title_full_unstemmed The Gini coefficient and discontinuity
title_short The Gini coefficient and discontinuity
title_sort gini coefficient and discontinuity
topic inequality
probability
math analysis
discontinuity
url https://www.tandfonline.com/doi/10.1080/23322039.2022.2072451
work_keys_str_mv AT jenspeterkristensen theginicoefficientanddiscontinuity
AT jenspeterkristensen ginicoefficientanddiscontinuity