Topic: Population Science
Kenji Itao from RIKEN in Japan studied 200 years of data from 237 countries and found two universal patterns that describe how fertility declines as societies develop. He discovered that despite differences in geography, culture, and economy, all countries follow these patterns.
Kenji Itao, a researcher at the RIKEN Center for Brain Science in Japan, looked at 200 years of demographic data from 237 countries and territories. He wanted to understand how fertility changes as societies develop. What he found was surprising: two universal mathematical laws that describe how fertility declines as societies grow.
Itao focused on the relationship between the number of births per 1,000 individuals (called the crude birth rate) and life expectancy at birth. He discovered that there are two distinct phases of demographic transition. The first phase is common in European countries until around 1950, where high child mortality and relatively high fertility were present. During this phase, improvements in life expectancy led to decreases in birth rates that maintained a balance between reproduction and survival.
In the second phase, which began around 1950 in many European countries, fertility and life expectancy follow a different universal law. Many developing countries also follow this law, sometimes without first passing through the earlier phase. Itao's model suggests that this shift reflects a change in how families invest their resources: from investing in having many children to investing in each child's education.
Itao developed a theoretical model based on a trade-off between reproduction and investment in education. He found that when survival is uncertain and child mortality is high, producing more offspring is an effective strategy for maintaining population and economic growth. However, when survival improves and economic opportunities expand, greater investment in each child's education becomes more economically advantageous.
Itao's work provides a new framework for understanding the demographic transition from high birth and death rates to longer lifespans and lower fertility.
Why It Matters
Understanding these universal patterns can help policymakers create effective strategies to address low fertility rates in developed countries, which is a major demographic challenge facing many nations.
Key Facts
- Kenji Itao studied 200 years of data from 237 countries and territories.
- He found two universal mathematical laws that describe how fertility declines as societies grow.
- The first phase of demographic transition is common in European countries until around 1950, where high child mortality and relatively high fertility were present.
- The second phase began around 1950 in many European countries, where fertility and life expectancy follow a different universal law.
- Itao's model suggests that families invest their resources differently in each phase: from having many children to investing in each child's education.
Key Terms
- Crude birth rate
- The number of births per 1,000 individuals
- Demographic transition
- The change from high birth and death rates to longer lifespans and lower fertility
Implications
Understanding these universal patterns can help policymakers create effective strategies to address low fertility rates in developed countries, which is a major demographic challenge facing many nations.
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