There is a literature on the size of nations, and therefore on their number, with some of the best work arguing for an emphasis on the tradeoff between heterogeneity and economies of scale. If we think of modern history as consisting of a long period of consolidation, or merger of nations, followed by a period of dismemberment, independence movements, or increased numerosity, then the story is one of technological changes that made increased size more valuable and then less valuable. (The facts can be disputed, if only because there is room to argue about the definition of a country. But this is not the place.) Alternatively, preferences might have become more homogeneous and then less so. If we think of preferences as including a taste for peace, or something else that might be cheaper to achieve with greater country size, then the analysis can get a bit circular even as it gains plausibility.