IMPACT OF TAXES AND TRANSFERS
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Enami, Lustig, Aranda, No. 25, November 2016<br />
1.1.1. Equalizing, Neutral, and Unequalizing Net Fiscal Systems: Conditions for the<br />
One Tax Case<br />
In this section, we review conditions that allow us to determine whether a fiscal system with<br />
only a single tax is equalizing, neutral, or uneqaulizing.<br />
Concentration and Lorenz Curves<br />
When the post-tax income Lorenz curve lies everywhere above the pre-tax income Lorenz<br />
curve, that is L X-T (p) ≥ L X (p), the tax is equalizing (and vice versa).<br />
Equation 3 implies that the post-tax income Lorenz curve lies completely above the pre-tax<br />
income Lorenz curve if and only if the concentration curve of taxes lies completely below the<br />
pre-tax income Lorenz curve. 5<br />
(4) L X-T (p) ≥ L X (p) ‹=› C T (p) ≤ L X (p) for all p, and with strict inequality for some p<br />
In other words, the distribution of post-tax income is less unequal than the pre-tax income<br />
distribution if and only if the tax is distributed more unequally than the income to which it<br />
applies, or put another way, if and only if the concentration curve of taxes lies completely<br />
below the pre-tax income Lorenz curve. This condition is shown on figure 1, which features<br />
the Lorenz curves for pre-tax and post-tax income and the concentration curve for taxes.<br />
In other words, if the average tax rate t(x) is increasing with income everywhere, then taxes are<br />
distributed more unequally than pre-tax income. Thus, an everywhere progressive tax will<br />
always be equalizing.<br />
Given equation 4, it is easy to see that the condition for a tax to be unequalizing is C T (p) ≥<br />
L X (p). This condition will occur if t(x) decreases with income, that is, if taxes are regressive<br />
everywhere. However, just like in the case of progressive taxes, it is not necessary for taxes to<br />
be regressive everywhere to be unequalizing. Finally, in the case of a proportional tax--that is,<br />
5 This is true because if 0 g 1, the weights by definition sum to one. Hence L X (p) must lie between C T (p) and<br />
C X-T (p) by necessity.<br />
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