Why do contemporary states fortify their borders? Modern military advancements have made such fortifications obsolete for security, yet scholars have offered no satisfactory alternative theory. I propose a theory of fortifications with economic motivations using a game-theoretic model where states compete to extract wealth over a shared population around a border. Such competition generates inefficiency and states have the option to construct fortifications to disrupt competition. Fortifications contain the wealth of citizens inside the state to be taxed and enforce efficient monopolies of extraction. States hence fortify when such profits outweigh short-term expenses. The models suggest that we should expect fortifications between territories of unequal economic capacities as richer states have more to lose from inefficient competition, complementing existing empirical results.

中文翻译：

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边境防御工事的经济来源


为什么当代国家要加强他们的边界？现代军事进步已经使这种防御工事为了安全而过时，但学者们没有提供令人满意的替代理论。我使用博弈论模型提出了一种具有经济动机的防御工事理论，其中各州竞争在边界周围的共享人口上榨取财富。这种竞争会导致效率低下，各州可以选择建造防御工事来破坏竞争。防御工事包含州内公民的财富，需要征税并实施有效的开采垄断。因此，当此类利润超过短期支出时，各州就会加强防御。这些模型表明，我们应该预期经济能力不平等的领土之间会出现防御工事，因为较富裕的国家会因低效竞争而损失更多，这与现有的实证结果相辅相成。