PRESTON CURVE POSTULATE

TAG: GS 3: ECONOMY

THE CONTEXT: The Preston curve refers to a certain empirical relationship that is witnessed between life expectancy and per capita income in a country.

EXPLANATION:

Preston Curve: Linking Income and Life Expectancy

• The Preston curve is an empirical relationship that describes the association between a country’s per capita income and the life expectancy of its population.
• It was first proposed by American sociologist Samuel H. Preston in his 1975 paper “The changing relation between mortality and level of economic development”.
• The curve demonstrates that individuals living in richer countries generally have longer life spans compared to those in poorer countries.

Relationship Between Income and Life Expectancy

• The key insights from the Preston curve are:
  • Positive Relationship:
    • There is a positive correlation between a country’s per capita income and the life expectancy of its population.
    • As a country’s income rises, its people tend to live longer on average.
  • Diminishing Returns:
    • The positive relationship between income and life expectancy is not linear.
    • The curve flattens out at higher income levels, indicating diminishing returns – further increases in income lead to smaller gains in life expectancy.
  • Upward Shift Over Time:
    • The Preston curve has shifted upwards over the 20th century, meaning that life expectancy has increased independently of changes in income.
    • Preston attributed this to factors like medical progress, education, public health services, and improved nutrition.

Criticisms and Limitations

• While the Preston curve is a well-established empirical relationship, it has faced some criticisms and limitations:
  • Lack of Longitudinal Evidence:
    • The curve is based on cross-country data, but some research suggests the relationship may not hold within individual countries over time.
    • Per capita incomes have generally diverged across countries, while life expectancies have converged.
  • Causality Concerns:
    • The relationship between income and health is complex, and the direction of causality is debated.
    • It is unclear whether higher incomes directly cause longer life expectancy, or if other factors drive both income growth and health improvements.
  • Oversimplification:
    • The curve may oversimplify the multifaceted determinants of health, as factors beyond just income, such as education, can also significantly impact life expectancy.

Implications and Interpretations

• The Preston curve has had several important implications:
  • Redistributive Policies:
    • The concave shape of the curve suggests that transferring income from the rich to the poor could increase the average health of a society, but only if the relationship is causal.
  • Economic Growth vs. Health Improvements:
    • Some economists have used the curve to argue that poor countries should focus on economic growth, as health improvements will follow.
    • However, others have emphasized the importance of direct investments in health and education.
  • Broadening Development Measures:
    • The curve has contributed to the inclusion of longevity in broader measures of economic and social welfare, beyond just income-based metrics.
  • The Preston curve highlights the strong empirical relationship between a country’s per capita income and the life expectancy of its population.
  • While the curve has faced some criticisms, it remains an influential framework for understanding the complex links between economic development and human health outcomes.

SOURCE: https://www.thehindu.com/specials/text-and-context/what-does-the-preston-curve-postulate/article68247927.ece