Core Concepts & Learning Goals
This chapter explores economic inequality, focusing on the distribution of income and wealth within a society. While markets can be efficient, they do not guarantee equitable outcomes. Understanding inequality is crucial for analyzing economic well-being and the impact of government policies.
After completing this section, you will be able to define the primary measures used to track economic inequality and explain the various factors that contribute to differences in income and wealth among individuals and groups.
Key Concepts Breakdown
1. Defining and Measuring Inequality
Economic inequality refers to the disparity in economic well-being among individuals in a group, among groups in a population, or between countries. It is most commonly measured in two ways: income inequality and wealth inequality.
Income Inequality: The extent to which income is distributed in an uneven manner among a population. Income is a flow of earnings from wages, salaries, interest, and other sources over a period of time (e.g., annually).
Wealth Inequality: The unequal distribution of a group's accumulated assets, minus liabilities. Wealth is a stock of assets owned at a specific point in time, including real estate, stocks, and savings. Wealth inequality is typically more pronounced than income inequality.
Data consistently shows that income levels and poverty rates vary significantly across different demographic groups, such as those defined by age, gender, and race, as well as across different countries. To quantify and compare these differences, economists use two primary tools.
The Lorenz Curve: A graphical representation of the distribution of income or wealth. It plots the cumulative percentage of total income received against the cumulative percentage of recipients, starting from the lowest-income individuals.
The Gini Coefficient: A numerical measure of inequality derived from the Lorenz curve. It is a single number ranging from 0 to 1, where 0 represents perfect equality (everyone has the same income) and 1 represents perfect inequality (one person has all the income). A higher Gini coefficient indicates greater inequality.
2. Sources of Income and Wealth Inequality
Inequality arises from a complex interplay of market forces, individual characteristics, and institutional structures.
Marginal Product and Factor Payments: In competitive factor markets, each factor of production (labor, capital, land) is compensated based on the value of its marginal product. For labor, this is the marginal revenue product of labor (MRPL). Individuals with skills that are in high demand and have a high MRPL will earn higher wages, contributing to income inequality.
Human and Social Capital:
Human Capital: The skills, knowledge, education, and experience that a person possesses. Individuals who invest in their human capital (e.g., through higher education or specialized training) tend to be more productive and command higher incomes.
Social Capital: The value derived from social networks and connections. Access to influential networks can provide advantages in securing jobs and business opportunities that are not available to others.
Tax Structures: The way a government levies taxes can either reduce or increase inequality.
Progressive Tax: A tax for which the percentage of income paid in taxes increases as income increases. Federal income taxes are a primary example. This structure tends to reduce post-tax income inequality.
Regressive Tax: A tax for which the percentage of income paid in taxes decreases as income increases. General sales taxes are often considered regressive because lower-income households spend a larger proportion of their income on taxed goods. This structure can worsen inequality.
| Feature | Progressive Tax | Regressive Tax |
|---|---|---|
| Definition | Average tax rate rises as income rises. | Average tax rate falls as income rises. |
| Burden | Falls more heavily on high-income earners. | Falls more heavily on low-income earners. |
| Effect on Inequality | Tends to decrease income inequality. | Tends to increase income inequality. |
| Example | U.S. Federal Income Tax | Sales Tax, Payroll Tax (up to a ceiling) |
Other Key Sources:
Inheritance: The transfer of wealth between generations can perpetuate and concentrate wealth, contributing significantly to wealth inequality.
Discrimination: When individuals face prejudice in labor markets based on race, gender, or other characteristics, their opportunities for education, employment, and wage growth can be limited, leading to persistent income gaps.
Access to Financial Markets: The ability to save, invest, and borrow is crucial for wealth accumulation. Disparities in access to banking, credit, and investment opportunities can prevent lower-income individuals from building assets.
Mobility: Economic mobility is the ability of an individual to change their income or wealth status. In societies with low mobility, a person's economic position is more likely to be determined by their starting point, entrenching inequality.
Bargaining Power: Differences in the ability to negotiate economic terms affect outcomes. For example, workers in a strong labor union may have more bargaining power to secure higher wages than non-unionized workers.
Graphical Analysis (Text-Only)
The Lorenz Curve
The Lorenz curve is a conceptual graph that illustrates income or wealth distribution. You will not be asked to draw one, but you must be able to interpret it.
Axes:
Vertical axis: Cumulative percentage of total income (from 0% to 100%).
Horizontal axis: Cumulative percentage of households (from 0% to 100%, ranked from poorest to richest).
Reference Line: The Line of Perfect Equality
This is a straight line with a slope of 1, running from the origin (0, 0) to the point (100, 100).
It represents a perfectly equal distribution. For example, along this line, the bottom 20% of households earn 20% of the income, the bottom 50% earn 50% of the income, and so on.
The Lorenz Curve
This curve plots the actual distribution of income.
It always starts at (0, 0) and ends at (100, 100).
Because inequality exists, the curve bows out, or sags, beneath the line of perfect equality. A point on the curve, such as (40, 10), would mean that the bottom 40% of households earn 10% of the total income.
Interpretation:
The degree of inequality is shown by the amount of "bowing" in the Lorenz curve.
The larger the area between the line of perfect equality and the Lorenz curve, the greater the income inequality in the society.
A policy that reduces inequality (like a progressive tax) would shift the Lorenz curve closer to the line of perfect equality. A policy that increases inequality would shift it further away.
Step-by-Step Example
Scenario: The government replaces its flat-rate income tax with a more progressive income tax system. Analyze the effect on income inequality.
Step 1: Identify the Policy's Direct Effect on Income.
A flat tax takes the same percentage of income from all households. A progressive tax takes a smaller percentage from low-income households and a larger percentage from high-income households. The policy change means that, after taxes, low-income households will keep a larger share of their income, and high-income households will keep a smaller share.
Step 2: Determine the Effect on Income Distribution.
The policy directly alters the distribution of disposable (after-tax) income. By design, it redistributes some income from higher earners to lower earners (or allows lower earners to keep more of their income than before). This makes the overall distribution of after-tax income more equal than it was under the flat tax system.
Step 3: Describe the Change Using the Lorenz Curve.
The initial Lorenz curve for after-tax income under the flat tax shows some degree of inequality (it bows away from the line of perfect equality). The new, more progressive tax system reduces this inequality. Therefore, the Lorenz curve for after-tax income will shift inward, moving closer to the line of perfect equality. The Gini coefficient, which measures the area between the line of equality and the Lorenz curve, would decrease, numerically indicating a reduction in inequality.
AP Exam Tips & Common Pitfalls
[FRQ Task]: Be prepared to explain how a specific policy (e.g., changes to taxes or transfer payments) or an economic event (e.g., globalization's effect on wages) impacts income inequality. You may be asked to describe the resulting shift in the Lorenz curve.
[MCQ Task]: Expect questions that ask you to identify sources of inequality (like differences in human capital) or to interpret the meaning of the Lorenz curve and Gini coefficient (e.g., a higher Gini coefficient means greater inequality).
[Common Pitfall ①]: Confusing income with wealth. Income is a flow of earnings over a period, while wealth is a stock of assets at a point in time. Policies that affect income (like an income tax change) may have a slower, indirect effect on wealth. Remember that wealth inequality is generally much more severe than income inequality.
[Common Pitfall ②]: Misinterpreting shifts in the Lorenz curve. A Lorenz curve that is closer to the 45-degree line of perfect equality represents less inequality. A curve that bows further away from the line represents more inequality. Do not confuse "a bigger curve" with "more income"; it means a more unequal distribution.
Key Vocabulary
Lorenz Curve: A graph on which the cumulative percentage of total national income is plotted against the cumulative percentage of the corresponding population. The extent to which the curve sags below a straight diagonal line indicates the degree of inequality.
Gini Coefficient: A numerical measure of income inequality, ranging from 0 (complete equality) to 1 (complete inequality). It is the ratio of the area between the Lorenz curve and the line of perfect equality to the total area under the line of perfect equality.
Human Capital: The stock of knowledge, skills, and abilities that determine a person's productivity and earning potential.
Progressive Tax: A tax system in which the average tax rate increases as income increases.
Regressive Tax: A tax system in which the average tax rate decreases as income increases.