demographics and military defense--3/24/2026

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Today's selection-- from Asia's Aging Security by Andrew Oros. The impact of declining fertility rates in Asia:

“The incredible population growth in the twentieth century was one of that century's defining hallmarks. Total world population nearly quadrupled, far exceeding the growth projected for the twenty-first century. It took all human history to reach the then–high mark of an estimated 1.6 billion people on the planet in 1900, but only one hundred years to add 4-6 billion more by the end of that century. Both popular writing and academic scholarship expressed widespread alarm at twentieth-century population growth, which was widely viewed as contributing to interstate conflict, threatening economic development of especially poorer countries, and perhaps even leading to a worldwide resource shortfall that would result in mass starvation. Many predictions both about how population demographics would shift and about the effects of these shifts on human security turned out to be incorrect.

“While this study focuses on the demographic challenges posed by twenty first-century population trends in the Indo-Pacific (which, as explained, are quite different from twentieth-century demographic shifts), it is important to understand how demographic change was understood to affect national security at that time, as insights and memories from the period still inform (sometimes, mistakenly) policy decisions and scholarship in this century. Moreover, instances of international conflict in the twentieth century have shaped existing international relations theory and, in several cases, remain conflict flashpoints in the Indo-Pacific in the twenty-first century (as discussed further in chapter 2).

“Brooks and her coauthors provide a useful summary of the world's overall demographic transition beginning even before the twentieth century that underscores the scale of recent change and implications for global security, drawing especially on Ronald Lee's 'The Demographic Transition: Three Centuries of Fundamental Change.' The first stage, they summarize, is the one that described all countries prior to around 1800, which 'displayed three characteristics: (1) very short lifespans (life expectancy was around twenty-seven years on average in all centuries prior to 1800); (2) very high birth rates (approximately six births per woman on average prior to 1800); and (3) relatively stable population sizes (as death rates more or less offset high fertility levels, with occasional short-term spikes in mortality caused by pandemics, famines, or wars).'

Countries by fertility rate as of 2024

“This first stage sets the demographic context for military-security strategies and experience for most of recorded human history and is one that is not at all relevant to the Indo-Pacific security environment today, where demographics across the entire region differ from this early stage.

“A second stage of demographic transition began in the Northern Hemisphere early in the nineteenth century, where mortality rates declined and thus average life expectancy increased due to numerous factors that Lee's summary explains. The third stage is when fertility rates decline in response to longer life expectancies (due especially to decreased infant mortality), but populations continue to grow due to longer life expectancies and still above-replacement birthrates. It was this stage that resulted in the ballooning of populations worldwide in the twentieth century and continues in some regions of the world in the twenty-first century (especially South and Western Asia and Sub-Saharan Africa).

“Late-stage rapid aging–the focus of this study–characterizes the fourth and fifth stages of the worldwide demographic transition underway. The fourth phase began to emerge particularly in advanced industrial countries in the 1970s, with several Asian countries on the leading edge of this change, where there is decline of fertility below the replacement level combined with long life expectancies, resulting in significant aging of generally stable population sizes. This stage occurred naturally as a result of personal decisions in Japan and elsewhere in the early 1970s as well as through China's One-Child Policy government mandate (officially from 1979 but less systematically prior to that as well).

“In the fifth stage of demographic transition theory, which only a few states have yet experienced (including China, Japan, Russia, South Korea, and Taiwan), fertility rates are so low that total population sizes begin to shrink, combined with even faster aging of the total population due to further increasing life expectancies. This new stage is projected to result in a proliferation of 'super-aged' societies worldwide by the mid-twenty-first century, including all the Northeast Asian region apart from Mongolia and others in the southern Indo-Pacific region as well. It also is projected to lead to a large number of states around the world experiencing total population shrinkage.

“To underscore the growing shift into this fifth stage of the global demographic transition, consider these 2024 statistics from the UN Population Division: In 63 countries and territories, containing 28 percent of the world's population in 2024, the size of the population peaked before 2024. In an additional 48 countries and territories, accounting for 10 percent of the world's population in 2054, population size is projected to peak between 2025 and 2054.7 Thus, worldwide, 111 countries and territories are projected to experience population shrinkage by 2024. This is the new demographic reality for the twenty-first century and one impetus for this study: to consider the security implications of this important shift in human development.

“The next section focuses on the first three stages of worldwide demographic transition, considering how international relations theory and security planners understood the impact of changing population characteristics through the ballooning population phase. The following section then contrasts theories based on twentieth-century experience with the new demographic realities of the twenty-first century IndoPacific, where nearly all traditional regional powers have entered the fourth and fifth stages of demographic transition, including the late-stage rapid-aging phenomenon.”

author:	Andrew Oros
title:	Asia's Aging Security: How Demographic Change Affects America's Allies and Adversaries (Contemporary Asia in the World)
publisher:	Columbia University Press
pages:	30-33