Niall Ferguson is the Milbank Family Senior Fellow at the Hoover Institution. He holds that when interest payments on the national debt eclipse defense spending, great powers struggle to maintain military strength and global influence. As US debt service surpasses defense outlays for the first time since the 1930s, Ferguson’s Law offers a stark warning about the fiscal foundations of American national power. Hoover has posted the video below expounding Ferguson’s Law.
Notes posted with the video cite Ferguson’s February 2025 Wall Street Journal essay “Debt Has Always Been the Ruin of Great Powers. Is the U.S. Next?” (behind the Journal paywall). In the essay Ferguson provides this formulation: “What I call Ferguson’s Law states that any great power that spends more on debt service than on defense risks ceasing to be a great power. The insight is not mine but originates with the Scottish political theorist Adam Ferguson, whose ‘Essay on the History of Civil Society’ (1767) brilliantly identified the perils of excessive public debt.”
Further: “Economists have long sought in vain a threshold that defines how much debt is too much. My own formulation of Adam Ferguson’s idea focuses our attention on the crucial historical relationship between debt service (interest plus the repayment of principal) and national security (expenditure on defense, including investment in research and development).”
Ferguson is the authorized biographer of Henry Kissinger and the author of 16 books, including The War of the World: Twentieth Century Conflict and the Descent of the West (2007). In 2015 The Week published a list of his favorite books here. Hoover’s biographical summary is posted here.
