Ferguson’s Law: Debt Service, Military Spending, and the Fiscal Limits of Power

ABSTRACT: Are there financial determinants of great-power decline and fall? This paper proposes “Ferguson’s Law,” which states that any great power that spends more on debt servicing than on defense risks ceasing to be a great power. The paper identifies the “Ferguson limit,” or the point at which interest payments exceed defense spending, as the tipping point after which the centripetal forces of the aggregate debt burden tend to pull apart the geopolitical grip of a great power. This is because the debt burden draws scarce resources towards itself, reducing the amount available for national security, and leaving the power increasingly vulnerable to military challenge. Using historical case studies that are analogous to the situation of the modern United States as the dominant global power, the paper shows that it is very rare but not unprecedented for a great power to return to the right side of the Ferguson limit. The paper is timely, as the United States began violating Ferguson’s Law for the first time in nearly a century in 2024.

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