A Lorenz curve plots running totals, not the shares themselves.
Kessland, 2024 (made-up data)
| Households | Share of income | Running total (plot this) |
|---|---|---|
| Poorest 20% | 6% | 6% |
| Second 20% | 11% | 6 + 11 = 17% |
| Middle 20% | 15% | 17 + 15 = 32% |
| Fourth 20% | 22% | 32 + 22 = 54% |
| Richest 20% | 46% | 54 + 46 = 100% |
Four steps
Poorest first
Put the groups in order, from the poorest fifth up.
Add them up
Keep a running total of the income shares.
Plot
Plot each total at 20, 40, 60, 80 and 100% of households.
Join and label
Join (0, 0) to (100, 100) through the points; label both axes.
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Now plot Kessland's running totals.
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The points to remember
- Plot the running total (17% at 40), not the share of that fifth (11%).
- Label the axes cumulative % of households and cumulative % of income, never wealth.
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Paper 3 asked this in November 2022, November 2025 and May 2026, for 2 marks each time.
Using the income distribution information in the table, construct a fully labelled Lorenz curve diagram for Kessland in 2024.
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How the 2 marks are given
| Mark | What earns it |
|---|---|
| 1 | Both axes labelled: cumulative % of households (or population) and cumulative % of income |
| 1 | The curve plotted accurately, at least at 40, 60 and 80% |