Prisoners of the Yen

The watch dashboard

Which road is Japan on?

The book argues Japan can hold only two of three goals — cheap debt service, a defended yen, normalized rates — and that the choice of which to sacrifice is legible in a handful of readings. These are those readings.

Prisoners of the Yen — book cover
The readings are market and official data. The framework for reading them comes from Prisoners of the Yen.

Paperback, out now. Prisoners of the Yen in English, 円の囚人 in Japanese. In Japan: English · 日本語版.

Scored in the matrix

USD/JPY, four-week change

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USD / JPY

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BOJ policy rate

1.25%

Highest since 1995 · hiked 18 Sep 2026 (7–2), effective 24 Sep · next meeting 29–30 Oct

Japan core CPI, y/y

1.7%

August 2026 · eighth month below the 2% target; ex-fresh-food-and-energy near 1.9%; the BOJ Outlook has inflation above target from the second half of FY2026 onward

10-year JGB yield

—%

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JGB 10s30s slope

—pts

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UST 10s30s slope

—pts

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Nikkei, from its 60-day high

—%

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Context — argued in the book, not scored

Nikkei 225

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Gold, $/oz (COMEX)

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Gold, ¥/oz

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Bitcoin, $

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Fed − BOJ policy spread

2.625pts

Fed 3.75–4.00% vs BOJ 1.25% · the gap that pulls the yen down

Japan gross debt

205% GDP

IMF 2026 · net ~134% · down from a 2020 peak of ~229% on the same vintage as inflation lifts nominal GDP

Market series: end-of-day closes, refreshed every 15 minutes. Policy and CPI readings are updated by hand after each release.

Reading the tape

The scenario map

Each row is an indicator; each column is the road it would point to. Track two above all: the yen's rate of change and the real policy rate — the Bank's rate less Japan's core CPI. Not the yen's level, which cannot tell credibility from liquidation, because both print a stronger yen. Fiscal stance is the swing that turns a given combination into A, B, or C.

Indicator Case A · consolidation Case B · debasement Case C · fiscal dominance
USD/JPY, four-week rate of change (two-tailed)Calm — under 2% either way, the level holding because policy is credible2–10% in either direction, sustained10% or more in either direction: weakness forces intervention and Treasury sales, strength forces the carry unwind
USD/JPY, post-interventionFirm and quiet — strength earned by discipline, not by positions closingDrifting weaker on the rate gapDefended by intervention rather than rates; FIMA-dependent, capital-flow measures appear
BOJ hike path vs. Japan core CPIHikes keep pace with or lead inflationHikes persistently lag inflationHikes halted or reversed despite an above-target print
10Y JGB yield & term premiumCompresses on restored credibilityElevated but orderlyDisorderly spike — or any new yield cap or purchase guidance
Long-JGB demand — 10s30s slopeAt or below its ten-year median, 0.77ptsSoft but functioning1.37pts or steeper — above the 95th percentile of the last decade; the super-long being abandoned
US duration — 10s30s slopeAt or below its ten-year median, 0.44ptsDrifting with the US fiscal story rather than Japan’s0.75pts or steeper — the long end underperforming on forced, price-insensitive selling
Fiscal stancePrimary-balance target restored; supplementary budgets shrinkSupplementary budgets stay large; debt-ratio metric retainedSpending sustained and the BOJ made to fund it
BOJ–government relationsIndependent, cooperativeQuietly accommodativeOpen friction; pressure on independence
Japan real wages vs. CPIPositive — relieves pressureNegative — sustains the squeezeSharply negative — a political forcing event

Reading the live feed against the matrix…

Current reading — 24 September 2026. Case B, unbroken. The Federal Reserve raised 25 basis points on the 16th and the Bank of Japan matched it on the 18th, 7–2, to 1.25%, effective the 24th. Because both moved, the policy differential ends the cycle where it began, at 2.625 points. With core CPI at 1.7%, the real policy rate is −0.45%, and the BOJ's own forecast has inflation rising clearly above 2%; a central bank that keeps hiking is still behind. Real wages have turned positive, up 2.4% in July from a year earlier, the seventh straight gain, so that row moves from B to A; one row doesn't move the case. Tokyo's first session with the new rate in force went the wrong way for a hike: the ten-year JGB touched 3.055% intraday, its highest in about 30 years, JGB futures tripped the Osaka Exchange's circuit breaker, and the yen traded near 158.7. On the Finance Ministry's constant-maturity measure, the ten-year closed at 3.073%, up 3.1% on the day and still inside the 5% line. Much of the pressure came from New York, where the ten-year Treasury is above 5.1%. The yen is 0.4% firmer over four weeks, back in the calm band after touching 152.90 on 8 September. The Nikkei closed at 65,514, up 495 points from the 18th, without the yen surge that marks a carry unwind. Fiscal policy stays expansionary: the FY2027 requests book debt service 17% higher. The tell that would move the reading to Case C is still not a weaker yen. It is any re-imposition of yield caps or purchase guidance, or a four-week yen move of 10% in either direction. The Bank of Japan decides again on 30 October.
This reading changes. The dashboard shows where Japan is now. The newsletter says what moved, why, and what would have to happen to move it again — monthly, and seven days after every Bank of Japan decision, in English and Japanese.