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IB DP Economics Study Notes

3.4.1 Measures of Inequality

In the vast arena of macroeconomics, comprehending the disparities in income and wealth is pivotal. This section delves deep into three primary instruments utilised by economists: the Lorenz Curve, the Gini Coefficient, and the Palma Ratio.

Lorenz Curve

The Lorenz Curve, a graphical representation, sheds light on the distribution of income or wealth in a particular society, offering insights into inequality.

What is the Lorenz Curve?

  • The graph's x-axis symbolises the cumulative percentage of the population, while the y-axis represents the cumulative percentage of income or wealth they hold.
  • The 45-degree line, colloquially referred to as the line of equality, paints a picture wherein each percentage of the population possesses an identical percentage of income or wealth.
A graph of Lorenz Curve

A graph illustrating Lorenz Curve.

Image courtesy of economicsonline

Interpreting the Lorenz Curve:

  • Below the Line of Equality: A Lorenz Curve resting below this line showcases an ideal scenario of perfect equality.
  • Above the Line of Equality: A Lorenz Curve distant from the line of equality suggests pronounced inequality.
  • It's paramount to understand that real-world Lorenz Curves can't be situated above the line of equality; this would imply a scenario where a small segment of the population holds over 100% of the wealth, which is nonsensical.

Real-world Implications and Significance:

  • The Lorenz Curve serves as a vital tool for economists and policymakers, enabling them to track fluctuations in income distribution across epochs or juxtapose the degrees of income or wealth inequality between diverse nations.
  • When the curve demonstrates significant divergence from the equality line, it might indicate deep-seated systemic issues or significant socioeconomic changes, warranting policymakers' attention.

Gini Coefficient

A numerical representation of income or wealth disparity within a nation, the Gini Coefficient is derived meticulously from the Lorenz Curve.

Delving into the Calculation:

  • The coefficient is the quotient of the area sandwiched between the Lorenz Curve and the line of equality to the whole region beneath the line of equality.
  • Its value oscillates between 0 and 1:
    • 0 is emblematic of impeccable equality (uniform income distribution amongst all).
    • 1 epitomises stark inequality (one individual amassing all the income, leaving others destitute).
A chart illustrating the Gini coefficient of G7 countries

Image courtesy of pewresearch

Harnessing the Gini Coefficient:

  • As a Comparative Measure: The Gini Coefficient's numerical nature allows for lucid comparisons across countries or enables tracking alterations within a nation over epochs.
  • Informed Policy Decisions: A soaring Gini Coefficient might prod governments to champion policies that endorse wealth or income redistribution, ensuring societal equilibrium. Understanding how factors such as Income Elasticity of Demand influence market dynamics can further inform these decisions.

Palma Ratio

Emerging as a novel measure of income inequality, the Palma Ratio casts a spotlight on the extreme ends of income distribution.

Understanding the Palma Ratio:

  • It's the quotient of the cumulative income of the topmost 10% of a population to the aggregate income of the bottom 40%.
  • By focusing on the ends of the distribution, the Palma Ratio underscores where the lion's share of income redistribution transpires.

Unpacking its Significance:

  • A Narrower Yet Poignant Focus: By honing in on the income brackets of the top 10% and bottom 40%, the Palma Ratio magnifies the areas where most income redistribution challenges occur.
  • Strategic Policy Implications: An escalated Palma Ratio signals a widening chasm between the affluent and the impoverished, necessitating bespoke economic strategies.

Real-world Applications and Insights:

  • The Palma Ratio's distinct concentration on the extremes of income distribution renders it particularly invaluable in nations marked by pronounced disparities between the elite and the underprivileged. By examining this ratio, governments and policymakers can strategise on more equitable fiscal policies, social welfare schemes, and other mechanisms to address the skew.

In the labyrinth of macroeconomics, tools such as the Lorenz Curve, Gini Coefficient, and Palma Ratio stand out as beacons. They don't merely offer theoretical scaffolding but endow students and policymakers with pragmatic insights, guiding their understanding and decisions in the intricate tapestry of wealth and income distribution across the globe. The negative externalities of production and the definition of externalities further accentuate the importance of addressing income inequality, as these factors often disproportionately affect the lower income segments. Additionally, the role of government in addressing market failures highlights the critical interventions needed to mitigate income disparity. Lastly, exploring income inequality directly elucidates the ramifications of unequal wealth distribution and underscores the necessity for robust measures of inequality like the Lorenz Curve, Gini Coefficient, and Palma Ratio.


Gini Coefficients vary significantly across countries, reflecting different levels of economic development, cultural norms, governance models, and policy priorities. Typically, developed nations have relatively low Gini Coefficients, indicating more equitable income distributions. However, exceptions exist, especially when policy changes alter income dynamics. Developing countries, on the other hand, can display a wide range of Gini values. Some, with extensive natural resources but concentrated ownership, might exhibit high inequality. Others, prioritising social welfare and redistribution, might achieve more equitable distributions. In essence, Gini Coefficients, when compared across countries, offer insights into each nation's socio-economic fabric.

Globalisation, with its multifaceted dimensions, can influence income distribution within countries. As economies open up, certain sectors might benefit more than others, often leading to increased income for those involved in globally competitive sectors. Conversely, industries less equipped to compete may see declining incomes. This disparity might result in an accentuated divide between the top 10% (who might be benefiting from globalisation) and the bottom 40% (who might be adversely affected). Thus, the Palma Ratio can be influenced by globalisation patterns, reflecting the nuanced impacts of global economic integration on different sectors of the population.

Yes, the Lorenz Curve, while valuable, isn't without its criticisms. One limitation is its inability to capture small-scale nuances in distribution. Two countries could have identical Lorenz Curves but very different internal distributions. Additionally, the Lorenz Curve doesn't differentiate between types of income or wealth, potentially masking disparities in sources of wealth. Also, since it's a snapshot tool, the Lorenz Curve might not capture dynamic changes over time effectively. Furthermore, the Lorenz Curve, being a relative measure, doesn't give insights into absolute levels of wealth or poverty, meaning it's possible for countries with different economic sizes but similar distributions to have similar curves.

The Lorenz Curve's start and end points represent the bounds of absolute equality and inequality. Starting at the origin implies that 0% of the population owns 0% of the wealth, establishing a baseline. Ending at the point representing the total population and total income means that 100% of the population holds 100% of the wealth, thereby setting an endpoint. Between these bounds, the curve’s shape conveys the reality of distribution. If every individual had equal income, the Lorenz Curve would be a straight 45-degree line. Any deviation from this line illustrates the disparities in distribution.

Real-world events, such as economic recessions, natural disasters, technological advancements, and policy changes, can have profound impacts on the Gini Coefficient. Economic downturns might widen income gaps if job losses disproportionately affect lower-income groups. Natural disasters can exacerbate inequalities, especially in countries lacking the resources for rapid recovery. Conversely, technological booms can either widen or narrow the gap, depending on the access and adaptability of various income groups. Policy changes, especially those related to taxation and welfare, can directly alter income distribution. Therefore, the Gini Coefficient isn't static; it reflects the ongoing interplay of socio-economic forces in a country.

Practice Questions

Elucidate the significance of the Lorenz Curve and the Gini Coefficient in analysing income inequality.

The Lorenz Curve, being a graphical representation, portrays the distribution of income or wealth in a society. Its distance from the line of equality highlights the extent of inequality prevalent. The more the curve veers away from this line, the greater the inequality. Conversely, the Gini Coefficient, a quantitative counterpart, calculates the disparity, with values ranging from 0 (perfect equality) to 1 (maximum inequality). Both tools, hand in hand, offer a comprehensive picture of income or wealth distribution, with the Lorenz Curve providing a visual aid and the Gini Coefficient giving a numerical measure, making them indispensable in socioeconomic analyses.

Why might the Palma Ratio be considered a more focused measure of income inequality than the Gini Coefficient?

The Palma Ratio zeros in on the two most telling segments of income distribution: the top 10% and the bottom 40%. This targeted approach accentuates the extremes, emphasising where the crux of income redistribution issues often lie. While the Gini Coefficient gives an overall snapshot of inequality in a society, the Palma Ratio illuminates the divide between the most affluent and the underprivileged. By spotlighting these extremes, the Palma Ratio offers a more concentrated lens to address stark disparities, making it a potentially sharper instrument in settings marked by pronounced inequities between the elite and the marginalised.

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Written by: Dave
Cambridge University - BA Hons Economics

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