Demographics features little to not at all in international relations theory. International power, economic might and population size can be found in indices of comprehensive national power This is mere description, not theory. Historians of international politics, occasionally, incorporate demographics into their narratives. A case can be made, for instance, that the significant population growth differential between Germany and France after the 1871 Franco-Prussian War contributed to the emergence of Germany’s semi-hegemonic position in continental Europe. With WWI approaching, demographic changes more directly impacted defence planning and policies and ultimately affected the fragile and complex balance of military power (Clark 2013).
Political scientists seem more attuned to demographics, as are economists. The political scientist’s youth bulge is the economist’s demographic dividend (or window). Rapid population increases combined with lack of economic opportunities may lead to increased risk of political instability (Gerling 2018). Political instability, civil wars and even terrorism in countries may be partly fuelled by strong population growth (e.g. Middle East, Africa, West Asia vs Latin America). Young men, in particular, are prone to take greater risks and in the face of economic challenges have less to lose than middle-aged men with mortgages (Tamas et al. 2019). Demographers are quite obviously even more attuned to the link between demographics and politics. Emmanuel Todd, a demographer and a teacher of mine, predicted the demise of the USSR on the basis of differential population growth rates among Soviet republics (Todd 1976).
Certain subfields in economics also take demographics seriously. There is the life-cycle hypothesis (Ando & Modigliani 1962) and, relatedly, the so-called demographic window. Changes in the age structure of a society and particularly in the dependency ratio may increase or decrease an economy’s saving/ investment/ growth potential, thereby also affecting the level of inflation/ interest rates/ economic growth (Bloom et al. 2003). While economists seem to agree that demographics is important, they, curiously, do not agree on whether, for example, population aging leads to higher or lower inflation (Goodhart & Pradhan 2017).
Historians studying the Middle Ages have argued that the plague lifted the land per capita ratio and hence real incomes. This in turn may have contributed to the economic and cultural flowering known as the Renaissance (Getz 1991) – not least by affecting the political-feudal power structure. Most economists attribute China’s rapid economic development in part to the introduction of a one-child policy in 1980. Perniciously, demographic change can also create the conditions for genocide. Strong population growth and concomitant land shortages at the very least preceded the Rwandan genocide of the mid-nineties (Diamond 2011).
Demographic factors have played an important role in the history of the United States and Brazil, or indeed any country in the Americas. In addition to forced migration (slave trade) and its social, economic and political impact, voluntary migration driven by wage differentials due to a more favourable land-labour ratio in the new world can be linked to US continental expansionism (Kagan 2007). Today, the legacy of US immigration may in part explain why public policies aimed at income redistribution are far less significant in the US than in other, more ethnically homogenous OECD countries (Alesina 2001).
Similarly, understanding Russian history is helped by an appreciation of demographic forces (and geography). Genghis Khan is supposed to have engaged in particularly brutal military tactics as his armies moved across the Eurasian landmass in the 13th century making it a point to kill or decimate most of the (male) population that got in their way. (This also allegedly explains why 0.5% of the world’s male population is descended from Genghis Khan (Nature 2015).) After the retreat of the Mongols, the road to Russian eastward expansion all the way to the Pacific was wide open, demographically speaking, at least in the south. Today, Russian about its demographic position in East Asia is factor affecting its policies towards China.
Rapid demographic change like the genocide of American Indians in the wake of the Spanish conquest may explain even bigger phenomena like climate change. The human destruction and subsequent civilizational collapse wrought on the indigenous populations by European colonisers led to large swaths of agricultural land not being cultivated. This contributed to a sharp drop in temperature around the world (e.g. Little Ice Age) and helped bring about political instability as far away as Asia (Koch et al. 2019). A combination of climate and disease agents can also help explain the stagnation and collapse of mighty empires (Harper 2019). Demographics sometimes also matters at the rhetorical level. Germany used Lebensraum rhetoric to justify territorial expansion (Tooze 2006). (If German policymakers actually believed in their own rhetoric, this would elevate rhetoric to a reason or even a cause (Jaeger 2020).)
Macro-structural changes often have macro-level effects. This does not mean, of course, that macro factors do not have micro effects and vice versa. It is important not succumb to the so-called "fallacy of identity" (Fischer 1970).) In practice, it is often difficult - or at least very arguable how - to tie macro-level causes (or background conditions) to micro-level effects. It is also true that historical events often cannot be properly understood unless they are put into a broader macro context. This was Fernand Braudel’s point about longue durée and histoire événementielle (Braudel & Wallerstein 2009). Macro-variables such as demographic change, climate and pandemic, geography provide the context within which event history happens. They do have some sort of causal effect, even if tying macro-conditions to micro-events can be difficult to do convincingly, for there is almost always both structure and agency involved (Jaeger 2020).
All of which is to say – I think – that demographic factors feature much more prominently in other fields of social and historical enquire than in international relations. Here are questions that might be worth exploring. Are countries experiencing demographic decline less likely to go to war (all other things equal)? Do youth bulges make states more inclined to engage in armed conflict (and why)? Might China’s one-child policy make society and state more reluctant to go to war? What impact will Russian demographic decline East have on Sino-Russian relations? How will projected rapid demographic growth in Africa and West Asia affect global politics? How will global population growth affect demand for and conflict over resources? What geopolitical and economic implications will demographic decline in Eastern Europe have on EU politics? It is quite possible that some of the questions have been tackled by researchers and related insults published in academic journals (e.g. Urdal 2012). Either way, how demographics affects international politics is, by and large, an understudied field, or at the very least deserves greater attention from both researchers and policy-makers.