JGB yields at forty-year highs reveal the mechanism by which sovereign bonds erode savings: the larger the debt grows, the more the central bank is forced to monetise it.
There is an experiment that has been running for decades, conducted involuntarily by one of the world’s largest economies. Japan has accumulated a public debt that, according to International Monetary Fund estimates, exceeds 200% of GDP – with broader measurements from Japan’s Ministry of Finance reaching figures close to 235-250% when all general government liabilities are included – has held rates at zero or below zero for years, has bought government securities in volumes large enough to become the primary holder of its own JGB (Japanese Government Bonds), and now finds itself with bond yields at their highest level in forty years. As noted by the Mises Institute, the Japanese government – led by Prime Minister Sanae Takaichi, who according to CNBC (May 2026) submitted a supplementary budget of approximately 19 billion dollars – wants to increase spending further, making it even harder to keep yields under control as deficits grow.
To understand the trap, one must start with the mechanics. A government issues sovereign bonds to finance the gap between tax revenues and public spending. Investors buy those bonds in exchange for a yield. As long as the market trusts the solvency of the state, yields remain low and the cost of debt is manageable. The problem arises when debt grows faster than the real economy: at that point the market demands higher yields to compensate for perceived risk, but higher yields increase interest expenditure, which in turn inflates the deficit, which requires even more issuance. It is a self-reinforcing cycle.
The Bank of Japan attempted to break this cycle through yield curve control – YCC – purchasing JGBs in sufficient volumes to hold long-term rates artificially low, a policy that ran from September 2016 to March 2024. The practical result is that the central bank monetised an enormous share of public debt, expanding its monetary base and weakening the yen. The Japanese saver who held ten-year bonds in their portfolio watched the nominal yield remain compressed while inflation eroded real purchasing power. The “safe” bond turned out to be a silent transfer of wealth from saver to state.
Financial repression as default policy
What the Japanese case illustrates with rare clarity is that financial repression – negative real yields imposed through monetary policy – is the instrument through which states manage debts that would otherwise be unsustainable. Economist Carmen Reinhart, together with M. Belen Sbrancia, documented how this mechanism was used systematically in the decades following the Second World War to reduce the public debt of developed countries: savers pay for debt reduction without an explicit default ever being declared. Japan over the past thirty years is the contemporary textbook case.
The structural point is that in this arrangement the central bank gradually loses its operational autonomy. When debt is large enough, raising rates significantly would render interest expenditure unsustainable for the public budget. The Bank of Japan experienced this directly: every attempt to normalise monetary policy produced turbulence in the bond market that forced a reversal or an extremely cautious pace. The problem concerns the architecture of the system: a central bank that finances sovereign debt protects the public budget at the expense of the currency’s value. The two objectives are in structural conflict, and over the long run one of them gives way. Historically, it is the second. On this point, the article on Greenspan and the Fed published on Atlas21 reaches the same conclusion by tracing the American path.
The divergence between nominal yield and real yield is the number that matters for savers. If a ten-year JGB yields 2% nominally but actual inflation is at 3%, the bond holder loses purchasing power every year, with the state’s guarantee. The guarantee, in this sense, is one of a certain and gradual loss rather than a sudden and visible one. States prefer this form of default because it is politically invisible: no official announcement, no credit event.
The structural deficit as a permanent condition
For holders of sovereign bonds in any country with similar dynamics – and Japan shares this trajectory with others, as the debt-to-GDP ratios of Italy, France, or the United States make clear – this arrangement has direct implications. The long-term government bond is an instrument whose real yield depends on the willingness and ability of the central bank to refrain from monetising the issuer’s debt. When issuer and monetary guarantor are one and the same, that willingness is subject to political pressures that the market cannot discipline effectively. The digital euro project – for which the European Parliament’s ECON committee approved its negotiating position in June 2026, targeting a possible issuance by 2029 – adds a further instrument of monetary control to this institutional chain.
