Birds of a Feather? The Co-Evolution of National Regimes and the International Diplomatic Exchange Network

Country pairs with diplomatic relations tend to have similar political regimes. This could be the result of a diffusion effect whereby the political regimes of connected countries become more similar over time. However, this similarity could also be the result of countries selecting diplomatic partners that are already similar. I test both explanations from a social network perspective using stochastic actor-oriented models and a co-evolution design. The results indicate that both effects are jointly present but with certain limitations. I find that autocratic countries preferentially select similar diplomatic partners, whereas democracies show no such preference. Diffusion of political regime characteristics via diplomatic ties only affects states with many democracies as diplomatic partners. All in all, after 1995, it was mainly selection mechanisms that were responsible for achieving and maintaining the observed levels of regime similarity within the diplomatic network.