Preston Curve

The Preston Curve is an insightful concept in understanding the relationship between economic development and health outcomes.

Summary of the Preston Curve

1. Concept Origin: The Preston Curve, introduced by Samuel H. Preston in his 1975 paper "The Changing Relation Between Mortality and Level of Economic Development," explores how life expectancy correlates with per capita income.
2. Core Observation: Preston observed that in wealthier countries, people generally live longer lives compared to those in poorer countries. This correlation is largely due to better healthcare, improved nutrition, cleaner environments, and other factors associated with higher income.
3. Initial Gains: As a country experiences economic growth, its per capita income rises. This initially leads to significant improvements in life expectancy as people access better nutrition, healthcare, and living conditions.
4. Broader Improvements: Along with increased income, other developmental indicators like infant and maternal mortality rates, educational attainment, and overall healthcare quality also tend to improve.
5. Example: In India, the average per capita income increased from around ₹9,000 per year in 1947 to ₹55,000 per year in 2011. During this period, life expectancy rose from 32 years to over 66 years, reflecting the positive impact of economic development on health.
6. Diminishing Returns: The Preston Curve indicates that while per capita income significantly boosts life expectancy in poorer countries, this relationship starts to level off in wealthier nations. Beyond a certain level of income, additional increases in per capita income yield diminishing returns in life expectancy. This plateau could be due to biological limits on human lifespan and the fact that other factors beyond income also play a critical role in health.

Additional Context

• Economic and Social Factors: While higher income improves life expectancy, the curve suggests that income alone isn't sufficient for further gains in health. Other factors, such as healthcare systems, social equality, and lifestyle choices, also play crucial roles.
• Policy Implications: Understanding the Preston Curve helps policymakers recognize that improving health outcomes in wealthy countries may require addressing non-economic factors, such as healthcare quality, social services, and environmental conditions.
• Global Perspectives: The Preston Curve also highlights disparities between countries. For instance, low-income countries may see more substantial improvements in health outcomes with economic growth compared to high-income countries where the returns on additional income are less pronounced.