America Rescued the Yen for Its Own Trillion in Treasuries, Not for Japan
The first US intervention in the yen in 28 years was officially a favor to an ally. The real calculation was to stop Japan from selling $1 trillion of US Treasuries to defend its currency — which would push up America's own cost of borrowing.
The video won't play here. Listen to the audio instead:
The argument · tap a timestamp to hear it
The Treasury Secretary's sticky note broke a 28-year taboo
The episode opens on an absurd detail: a sticky note carried by US Treasury Secretary Bessent into a cabinet meeting, reading "buy yen, $5-10 billion," with the currency code JPY thoughtfully appended. Trump later explained it aboard Air Force One as doing a friend a favor, and even brought up Pearl Harbor. The genuinely strange thing is not the note but the nature of the act: the last time the US Treasury stepped in to support the yen was 1998, 28 years ago. By convention a Treasury Secretary does not do this, which makes it worth asking what actually happened.
— Patrick BoyleCarry trade profits are not free money but a fee for holding the grenade
There is no mystery to the mechanics of yen weakness. The Fed raised rates to roughly 3.75% to fight inflation, while the Bank of Japan held at zero for years and only recently moved to 1%. That enormous gap created the global carry trade: borrow yen in Tokyo at almost no cost, swap into dollars, and buy Treasuries paying around 4%. The textbooks say this should not produce a free lunch — the low-yielding currency ought to appreciate by exactly enough to cancel the rate differential. For years the market has done the opposite, and economics calls the gap the forward premium puzzle. The more popular explanation is that what you earn is not free money but a commission for holding the grenade on everyone's behalf. When it blows up, everybody runs for the exit on the same day, and the yen appreciates violently.
— Patrick BoyleAmerica bailed out the currency of a country on its own watchlist
The US Treasury's official position has not changed in decades: it does not intervene in exchange rates, it lets the market set value, and intervention is only a short-term band-aid. To police everyone else, it publishes a report every six months naming trading partners that manipulate their currencies. The latest report, in July of this year, listed 10 countries, and Japan was on it. Yet in that very same month the US Treasury went into the market itself to help Japan bid the yen up. Strictly speaking, what the report criticizes is holding a currency down to push exports, and this time the intervention pushed the yen up. But spending American taxpayers' money to move a currency you are actively monitoring makes it plain that the rules are there to constrain other people.
— Patrick BoyleWashington funded the yen rescue by quietly selling euros, not dollars
The execution is stranger still. When the New York Fed placed the orders with Goldman Sachs and Morgan Stanley on the Treasury's behalf, what it sold was not dollars but euros — and the European Central Bank was kept in the dark. The bulk of the euro assets in the US Exchange Stabilization Fund are French government bonds, so there is a strong chance America was in effect dumping a batch of French sovereign debt. A senior ECB official described this to the FT as "an unprecedented breach of central bank etiquette," and the IMF handbook explicitly advises central banks not to intervene in other countries' currencies. It amounts to driving off in your neighbor's car without asking, hitting a tree, and then explaining to him why his premium is going up.
— Patrick BoyleThe rescue was aimed at Japan's trillion in Treasuries, not at the yen
Friendship with Tokyo is not the point; America's own borrowing costs are. Japan is the largest foreign holder of US government debt, with more than $1 trillion. If Japan spends another $50 billion or $80 billion defending the yen, the most convenient way to raise the money is to sell Treasuries — and heavy selling would push Treasury prices down and yields up. That is exactly what Bessent most fears, which is why he wants to help Japan steady the yen. His résumé makes it more ironic: in 1992 he was at the Soros fund and watched the Bank of England get picked off, and he later made his name shorting the yen. Now, sitting in the US Treasury Secretary's chair, the thing he is defending against is precisely the playbook he ran 30 years ago.
— Patrick BoyleA Treasury Secretary should not place directional bets through debt issuance
For most of the past two years Bessent has tilted issuance toward short-term bills and been unwilling to issue long bonds. The stated reason is that long-end rates are high right now, so there is no need to lock in for 30 years. Underneath it is a directional bet — a wager that inflation comes down, long rates fall, and the debt can then be swapped into long bonds. That bet is fine coming from a hedge fund, but not from a Treasury Secretary, whose job is not to guess rates but to fund the government regularly and predictably. Unfortunately rates have not fallen: the 10-year has risen to roughly 4.6%, and the 30-year has broken 5%. As long as rates do not come down, his funding strategy is stuck in a loop of rolling short-dated paper at ever higher cost.
— Patrick Boyle$88 billion bought two weeks, and half the gain was given back
The intervention did work at first: at the end of July the US and Japanese authorities spent roughly $88 billion over two days, and the yen went from around 164 to 155, a move of about 5%. Within two weeks it had slid back to 159, giving up half of that gain. The reason is plain — the FX market trades trillions of dollars a day, and $88 billion is small change. Obstfeld calls this set of contradictory policies cakeism: America wants a weak dollar but no inflation, low borrowing costs alongside enormous deficits, and Japan to keep buying Treasuries while the yen strengthens. America's own tariffs and its pressure on Japan to invest in the US are themselves pushing the yen down. It is bailing water out of the boat while drilling holes in the hull.
— Patrick BoyleTreasuries are no longer scarce, and that is the real foundation here
The real foundation of this drama is not the yen but the scarcity of US Treasuries. A paper by Harvard professor Wenxin Du finds that the convenience yield the world pays for the safety and liquidity of Treasuries has been narrowing for decades and has recently vanished, even turning negative. The cause is supply: too many Treasuries have been issued, and they are no longer scarce. Thursday's 30-year auction cleared at 5.22%, already the highest 30-year borrowing cost for the US since 2001. If the goal is a stronger yen, the cleanest route is for the Bank of Japan to raise rates. But Japanese government debt is already above 200% of GDP, debt service eats a quarter of government spending, and the new prime minister is opposed to hikes. Intervention does not change the trend; at most it buys a few days.
— Patrick BoyleIn their own words · checked verbatim
The last time it stepped into the market to prop up the yen was 1998. So when it happens again after 28 years, it's worth asking why.
Patrick Boyle3:11
The carry trade works right up until the point where it doesn't, and when it stops working, it stops for everyone, on the same afternoon.
Patrick Boyle5:14
It's a bit like gauging the British economy by the price of a burrito. You'll get a number, it just won't mean very much.
Patrick Boyle8:21
It's the financial equivalent of showing up at your neighbor's house, borrowing their car without asking, crashing it into a tree, and then calling them the next day to explain why their insurance premium is going up.
Patrick Boyle12:31
Rates don't go to zero because things are going well. They go to zero because something has broken horribly.
Patrick Boyle17:52
It's a man bailing water out of a boat that he's also enthusiastically drilling holes in.
Patrick Boyle25:09
When you flood the market with something it stops being precious. So, the free money the United States used to get for being exceptional is draining away.
Patrick Boyle27:21
If your bonds have stopped being magically special and your single largest foreign customer starts selling them, your borrowing costs rise.
Patrick Boyle28:22
Figures
| Intervention size on Bessent's sticky note | $5-10 billion | 1:08 |
| Last time the US directly stepped in to support the yen | 1998 (28 years ago) | 3:11 |
| US-Japan policy rate gap | Fed at roughly 3.75% vs Bank of Japan at 0% (later raised to 1%) | 4:14 |
| Size of the global yen carry trade | More than $4 trillion, larger than India's GDP | 5:14 |
| Curry rice parity implies the yen is undervalued | 62 yen to the dollar vs 159 actual; roughly 60% undervalued; about 80 yen on the Big Mac measure | 7:16 |
| Treasury yields over the same period | 10-year at roughly 4.6%, 30-year above 5% | 19:56 |
| Scale and effect of the US-Japan intervention | Roughly $88 billion; the yen rose about 5% to 155 at one point, then fell back to 159 within two weeks | 23:09 |
| Japan's debt and debt service burden | Debt above 200% of GDP, debt service accounting for 1/4 of government spending | 29:26 |
Glossary
- carry trade
- Borrowing in a low-rate currency and swapping into higher-yielding assets to pocket the spread; the yen is the world's funding currency.
- forward premium puzzle
- Theory says the low-rate currency should appreciate until the rate differential is cancelled out; reality has diverged from that for years.
- Cakeism
- Wanting everything at once and refusing to pay any price; used here to describe the self-contradiction in US fiscal policy.
- Treasury Convenience Yield
- The extra yield investors give up for the safety and liquidity of US Treasuries, now compressed into negative territory.
How to listen
Macro traders who follow Treasury yields and global liquidity, corporate treasurers with cross-border funding in Japan and the US, and investors watching fiscal sustainability.
The Pearl Harbor joke and the lead-in before 2:09 can be skipped.