Talk:Gini coefficient

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Formula for the Gini coefficient

It seems to me the current formula in the article might be slightly incorrect. Here is the current formula:

$G=\frac{\sum _{i=1}^n\sum _{j=1}^n|x_i-x_j|}{2\sum _{i=1}^n\sum _{j=1}^n{x}_j}=\frac{\sum _{i=1}^n\sum _{j=1}^n|x_i-x_j|}{2n\sum _{j=1}^n{x}_j}=\frac{\sum _{i=1}^n\sum _{j=1}^n|x_i-x_j|}{2n^2\overline{x}}$

Specifically, the current numerator suggests it would include each person's difference from themself, i.e., $x_i-x_j$, where $i=j$. However, if $j$ is defined as the set of all other persons who aren't $i$, then the upper limit of $j$'s index ought to be $n-1$. Thus, I believe the numerator ought to be:

$\sum _{i=1}^n\sum _{j=1}^{n-1}|x_i-x_j|$

Moreover, I propose that the article be updated to explicitly define $j$.

Lastly, I'm not sure whether the denominator needs any updating. MosesRivera100 (talk) 19:07, 7 September 2023 (UTC)

These formulas added later may be wrong. Take $x_1=1;x_2=0$

Using these would give: $G=\frac{1}{2n^2}\frac{\sum _i\sum _j|x_i-x_j|}{\overline{x}}=\frac{1}{8}\times \frac{|1-0|+|0-1|}{0.5}=\frac{1}{2}$

Now use $G=\frac{\text{mean absolute difference}}{\text{mean}}=\frac{\overline{\mathrm{\Delta }}}{\overline{x}}$

Where $\overline{\mathrm{\Delta }}=\frac{1}{n}\sum _i\sum _{j>i}|x_i-x_j|=\frac{1}{2n}\sum _i\sum _j|x_i-x_j|$

and $\overline{x}=\frac{1}{n}\sum _i{x}_i$

You'll get the correct value of 1. In this case, $G=\frac{\sum _i\sum _j|x_i-x_j|}{2\sum _i{x}_i}$ 2804:1998:421:F201:88E7:6514:10BF:CCDF (talk) 19:57, 25 June 2024 (UTC)

The calculation section is more confusing than...

Mathworld's article on the Gini Coefficient: https://mathworld.wolfram.com/GiniCoefficient.html Am I missing something? This wiki article makes it seem like the Gini coefficient is difficult to use and fraught with pitfalls without giving many concrete definitions, while the Mathworld reference has two easy-to-understand formulas. What's up with that? 24.228.174.225 (talk) 21:51, 5 August 2024 (UTC)

Gini Coefficient doesn't measure wealth inequality

Gini Coefficient only measures income inequality and not wealth inequality and text(s) saying that should be removed.

The source [2] for the statement that

"Gini index or Gini ratio, is a measure of statistical dispersion intended to represent the income inequality, the wealth inequality, or the consumption inequality" doesn't even say or imply that.

Wealth inequality is always greater than income inequality, and Gini only measures income inequality. It is very misleading to say/imply that wealth inequality is at the same level as income inequality. Egalitaristen (talk) 20:15, 4 March 2025 (UTC)