Questions: Measuring and Understanding Income Inequality

Question 1

Countries A and B both have a GDP per capita of $12,000. Country A has a Gini coefficient of 0.28; Country B has a Gini coefficient of 0.58. A policymaker claims the two countries have equivalent living standards because their averages are identical. What critical information does this claim miss?

• A. GDP per capita is adjusted for purchasing power in Country A but not in Country B, making the comparison invalid
• B. The Gini coefficient shows that Country B's income is far more concentrated at the top, meaning most households likely have incomes well below $12,000 while a small elite earns far above it — the average conceals vastly different typical lived experiences
• C. Country B's higher Gini means it is growing faster, which will reduce inequality in the long run through the Kuznets curve
• D. The policymaker is correct — Gini only measures distribution, not welfare, so the same GDP per capita implies identical aggregate welfare

Answer: (B)

GDP per capita is an average, and averages can be deeply misleading when distribution is skewed. A Gini of 0.58 (typical of highly unequal countries) means the Lorenz curve bows far below the 45-degree equality line — the bottom half of the population holds a small fraction of total income. Most households live on far less than $12,000 while income concentrates at the top. Equal averages can coexist with radically different distributions: the Gini coefficient is precisely the tool for seeing inside the average to evaluate actual distributional equality.

Question 2

Why has the Palma ratio (top 10% share divided by bottom 40% share) gained favor as a complement to the Gini coefficient?

• A. Because it is easier to calculate than the Gini and requires no graphical representation of a Lorenz curve
• B. Because the middle 50% of the income distribution is relatively stable across countries and time — most inequality variation occurs in the tails — so the Palma ratio focuses attention where distributional differences are actually largest
• C. Because international agencies like the World Bank officially adopted it as their primary inequality metric in 2010
• D. Because it corrects a known mathematical error in the Gini coefficient that makes it underestimate inequality in developing countries

Answer: (B)

The insight behind the Palma ratio is empirical: across many countries and time periods, the middle 50% of the income distribution consistently holds roughly half of national income. Most of the cross-country variation in inequality shows up at the extremes — the richest 10% and the poorest 40%. By directly comparing these extremes, the Palma ratio focuses attention on where real differences lie. It is also intuitively interpretable: a Palma of 3 means the richest 10% earn three times as much as the poorest 40% combined.

Question 3

A Gini coefficient of 0.5 means the top 50% of earners hold exactly 50% of most income.

• T. True
• F. False

Answer: False

The Gini coefficient is not a percentile share ratio — it measures the area between the Lorenz curve and the 45-degree line of perfect equality, divided by the total area under the 45-degree line. A Gini of 0.5 means this ratio equals 0.5, which is consistent with many different shapes of the Lorenz curve and many different percentile shares. The 50th percentile income share is a separate statistic. In highly unequal economies, the top 50% can easily hold 80% or more of income while the Gini is around 0.5.

Question 4

Two countries with identical GDP per capita can have very different distributions of income, as captured by differences in their Gini coefficients.

• T. True
• F. False

Answer: True

This is the foundational motivation for inequality measurement. GDP per capita divides total income by population, but this average is consistent with any distribution from perfect equality to extreme concentration. The Gini coefficient and Lorenz curve reveal the shape of the distribution independent of the mean. A country where everyone earns $10,000 and a country where one person earns $1 million and ninety-nine earn roughly $1,000 can have the same GDP per capita but vastly different Gini coefficients (approaching 0 and 1, respectively).

Question 5

Through what economic mechanisms does high income inequality potentially slow economic growth — beyond simply being unfair?

Model answer: High inequality can suppress growth through several reinforcing channels. First, it undermines human capital accumulation: poor households cannot invest in education, nutrition, and health for their children, reducing the economy's future productivity. Second, it weakens domestic demand — when income concentrates at the top, where marginal propensity to consume is lower, consumer markets remain thin and firms serving mass markets face limited opportunities. Third, it erodes social cohesion and institutional quality, breeding corruption, rent-seeking, and political instability that divert resources from productive use. Fourth, extreme inequality can produce political capture, where elites shape policy to protect their position rather than promote broad-based investment.

These channels explain why highly unequal countries often experience slower or more fragile growth — the distributional issue is not just ethical but functional. The cross-regional comparison in the topic illustrates this: East Asian economies combined rapid growth with relatively low inequality partly through land reform, broad education investment, and manufacturing-led employment; Latin American economies with historically high inequality (rooted in colonial land concentration) have faced more persistent growth challenges. Inequality is not an inevitable consequence of development; it is shaped by policies and institutions.