Human impact on ecological systems has made population size, density, land use, and settlement locations priority concerns among ecologists and the environmental community. Economic and political demographers, on the other hand, have focused their research on understanding how the age distribution of a country’s residents—known as age structure—statistically influences the ability to advance social, economic, and political development. Their conclusion: while its influence on development is often indirect, age structure continues to be under-appreciated and poorly understood by economists and political scientists.
Until worries over population aging spread through the industrial world, most social scientists remained unaware of the age-structural transition—the shift, driven largely by fertility decline, from a population that is dominated principally by young people to one where much older adults are in the majority (Fig. 1). Demographers have shown that the transition’s most advantageous distributions emerge during the intermediate phase (see Fig. 1), near the middle of the transition, in what the UN Population Division has called the demographic window. Therefore, the pace of social and economic development has largely been set by a country’s ability to exit the difficult youthful phase of the transition and enter the demographic window—an achievement requiring a country’s total fertility rate (an estimate of the average number of children a woman will bear during her lifetime) to decline from between four and seven children per woman, to less than three (Fig. 2).
Unfortunately for countries and their societies, this journey doesn’t end when they make it to the demographic window. After youth bulges become worker bulges and ultimately shift toward the retirement ages, childbearing has typically continued to decline, and populations have drifted beyond the end of the demographic window—a situation that has befallen Japan and nearly all of Europe and will soon sweep across East Asia. How countries that sustain very low fertility (below 1.5 children per woman) perform in the future, when older adults comprise more than one-third of all residents, will likely depend on how effectively their governments, businesses, and civil society capitalized on investment opportunities during their journey through the demographic window and how well their institutions balance their obligations to both young and old, against the demands of workers and the needs of the economy.
Foreign affairs analysts and policymakers should note that there are, of course, exceptions to this transition’s development model. Outliers can be found among countries with fewer than 5 million residents (mostly small island states) and among countries endowed with substantial wealth from oil and minerals or from income sent by relatives overseas.
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Age-structure’s statistical pace-setting power can be observed (Fig. 3) in the otherwise uneven progress of the UN Development Program’s Human Development Index, or HDI, which integrates three of the most fundamental indications of development: life expectancy at birth, education, and per-capita income. The real milestones of development—entry into the HDI’s high and very high categories—generally occur while countries pass through the demographic window, when the population’s median age (the age of person for whom half the population is younger) is between 26 and 40 years. Most youthful countries—those with a median age of 25 years or less—generally lag behind the global HDI average.
So, does population aging affect human development? While countries with mature populations that are leaving, or have left, the demographic window typically face slower rates of economic growth, rising debt, and are pressured to make unpopular fiscal reforms, so far, their HDI scores show no apparent sign of decline. Whether these stresses ultimately reveal themselves in fundamental measures of development, or among indicators of governance or assessments of democracy, remains to be seen.
Richard Cincotta, PhD, is a Wilson Center global fellow. He is the 2023 recipient of the Myron Weiner Award, which honors career contributions to political demography, from the International Studies Association's Political Demography & Geography Section. His research focuses on the influence of the age-structural transition on political, institutional, and environmental conditions. His writing on demography has appeared in Foreign Policy, Current History, Nature, and Science, and he contributed to four of the National Intelligence Council’s Global Trends reports.
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