a certain quintile. The income distribution in 1980 was closer to the perfect equality line than the income

distribution in 2020—that is, the U.S. income distribution became more unequal over time.

Every Lorenz curve diagram begins with a line sloping up at a 45-degree angle. We show it as a dashed line in

Figure 15.8. The points along this line show what perfect equality of the income distribution looks like. It would

mean, for example, that the bottom 20% of the income distribution receives 20% of the total income, the

bottom 40% gets 40% of total income, and so on. The other lines reflect actual U.S. data on inequality for 1980

and 2020.

The trick in graphing a Lorenz curve is that you must change the shares of income for each specific quintile,

which we show in the first and third columns of numbers in Table 15.6, into cumulative income, which we

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15.4 • Income Inequality: Measurement and Causes 373
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