RODNEY HIDE: What is the New Zealand government's Debt Limit?

Sir Niall Ferguson’s “Ferguson limit” is the point at which a nation spends more on debt interest than on defence. Cross it and the fiscal arithmetic begins to erode the ability to project power or even maintain basic sovereignty. The United States crossed it for the first time in nearly a century in 2024. New Zealand beat them to it.

Our latest numbers are damning. Core Crown interest payments are running at around $8.9 billion a year. Defence spending sits at roughly $3.3 billion. We are not close. We are already deep into Ferguson territory. Interest alone now dwarfs law and order spending as well. The debt service bill is larger than entire departments.

This is not a temporary spike. It is the logical result of decades of structural deficits, an ageing population, low fertility and the political cowardice that MMP encourages. Even under a centre-right Coalition we are still adding to the pile. Support parties demand their slice. Operating allowances get eaten by pre-commitments. The can gets kicked.

Ferguson’s warning is clear: once interest crowds out defence and essential services, the decline accelerates. Resources flow to bondholders instead of capability. Strategic choices narrow. The state becomes a pension administrator with a military hobby on the side.

Compare us to Australia. Their debt-to-GDP is lower, their interest burden more manageable and their defence spending more credible relative to the books. The UK and Canada are strained but still have more fiscal headroom than we do. Small, open economies like New Zealand cannot afford to live like Italy or Greece. Yet here we are.

The Rogernomics era under First Past the Post showed what is possible. A government with a majority could take hard decisions, cut spending, deregulate and bring the books back toward balance. MMP makes that almost impossible. Every Budget is a negotiation. Every cut is a veto opportunity for a support partner looking for political capital.

We crossed Ferguson’s limit with our eyes open. The data has been screaming for years. The solution is not another fiscal rule or another clever accounting trick. It is structural. Cut non-core spending ruthlessly. Sell assets that have no strategic justification. Flatten taxes to encourage growth instead of more borrowing. Most importantly, face the demographic reality: without higher fertility and a culture that values children, the welfare state is unsustainable.

New Zealand once led the world in reform. We can do it again — but only if we stop pretending coalitions can deliver discipline. They cannot. The debt interest bill is the proof. Time to choose: keep kicking the can or fix the system that keeps filling it. The Ferguson limit is not a warning. It is the verdict.

Rodney Hide is a former Minister and ACT party leader