Study finds shared mathematical pattern behind global fertility decline

ANBAR, Iraq — A researcher at Japan's RIKEN Center for Brain Science has identified a recurring demographic pattern that appears to shape fertility rates across cultures, political systems and geographies. Kenji Itou analyzed birth and death data from 237 countries and regions between 1800 and 2020, examining how societies have moved from high birth and death rates to longer-lived populations with fewer children. The study describes two main stages. Before 1950, gains in life expectancy in Europe were offset by gradual declines in birth rates, leaving overall population growth relatively stable. After 1950, families began choosing to have fewer children while investing more in average income and education, a pattern Itou says is now visible in many developing countries as well. Itou framed the shift as a balance between the number of children a family has and the investment made in their education. Lower costs of raising and educating children, greater social mobility and longer lifespans accelerated the transition, according to the research. The study also argues that fertility decline in advanced economies is not inevitable. Itou said policies that ease the financial burden of raising and educating children could help stabilize birth rates. He added that the findings offer a framework linking statistical physics, evolutionary science and demography to better understand the evolution of human societies.