The rapid expansion of international non-governmental organizations (INGOs) numbers in the last half-century is usually explained to be a result of decolonization, globalization, and/or increase in the number of global issues. One additional hypothesis, which has not been discussed in the political science literature, is suggested by the demographic-structural theory. According to this hypothesis, the acceleration in INGO numbers was caused by the post-war baby boom and a crisis in the credential system. This study finds that cyclical increases in INGO numbers were preceded by expansions in the 30–39 cohort. Interestingly, the mean age of leaders across 12 international governmental institutions also oscillated, but with a lag (thus correlated with expansions of the 55–64 cohort). Thus evidence supports the idea that demographic-structural mechanisms contributed to the surge in INGO numbers during the last 50 years as a by-product of intraelite competition.

A large dataset is used to map the historical spread of iron use across Afro-Eurasia using a number of different methodologies. Traditional dates for the beginning of what archaeologists call the “Iron Age” in each region are unacceptable because they are imprecise and the dates themselves are reached on the basis of different methodologies. The author maps the spread of iron with a primary focus on its acceleration in use across many object classes. Three additional maps are also provided: the first critical use of iron for cutting tool or weapon, the spread of iron helmets and the spread of high-quality steel swords. While many of the maps are at the experimental stage, the results give a unique insight into technological change across history and can be used to test predictive models of historical change. As the mapping of the rise and spread of a technology has rarely or never been done before on this scale, the maps, the methodologies used, and the problems encountered provide a fork in the scholarship for more accurate and detailed successors.

Military technology is one of the most important factors affecting the evolution of complex societies. In particular, mounted warfare, the use of horse-riders in military operations, revolutionized war as it spread to different parts of Eurasia and Africa during the Ancient and Medieval eras, and to the Americas during the Early Modern period. Here we use a variety of sources to map this spread.