The August 2024 Yen Carry Unwind: A Six-Day Anatomy

Between July 31 and August 5, 2024, a Bank of Japan rate decision and a weaker-than-expected US jobs report landed on top of a carry trade that had already been getting less comfortable to hold since early July, producing an unusually sharp, fast market event: Japan's TOPIX index fell 12 percent in a single day, the VIX spiked to its highest level since the COVID crash, and the S&P 500 briefly showed its worst two-day stretch in years, before most of the move reversed within about a week. This piece walks through the sequence in order, including the part of it that started before the two headline triggers.

The buildup, since spring. The Bank of Japan had already been signaling a shift away from years of near-zero rates since March 2024, when it ended its negative-rate policy. By early July, yen weakness that had persisted through the spring began to reverse on market chatter about possible currency intervention by Japanese authorities, and Japanese equities, which had been strong for much of the year, started to soften. BIS evidence on hedge-fund positioning suggests several strategies had become increasingly crowded around the carry trade over at least the preceding year, though the data on the exact scale is inherently imprecise, meaning a large amount of borrowed-yen exposure was already sitting on shakier ground before either of the two events usually cited as the trigger.

July 31: the Bank of Japan moves. Against that backdrop, the Bank of Japan raised its policy rate to around 0.25 percent, a larger and more hawkish-sounding move than some investors had expected. The yen strengthened further against the dollar in response. On its own, this was a notable but not alarming policy decision, Japan's Nikkei 225 initially closed higher on the day.

August 2: a weak US jobs report. The US employment report for July, released August 2, showed nonfarm payrolls growing by a much smaller amount than expected and the unemployment rate rising to 4.3 percent, a reading that triggered the Sahm Rule, a widely watched recession-signaling indicator based on how fast the unemployment rate has risen from its recent low. That added a second, independent source of concern on top of the BOJ move, and on top of positioning that was already unwinding.

The mechanism connecting the pieces. Years of near-zero Japanese rates had made the yen a popular funding currency, borrowed cheaply through loans, swaps, or forwards and used to invest in higher-yielding assets elsewhere; the exact routes varied across participants and aren't fully observable. What matters for the mechanism is the relative economics: the BOJ move and shifting rate expectations narrowed the expected advantage of being short yen, while the US growth scare and rising volatility made the risk side of the trade considerably worse. Carry became less rewarding at exactly the moment it became more dangerous, on top of a position that had already begun shrinking in early July. Unwinding means buying back yen to close out that exposure, which pushes the currency higher, which further squeezes anyone still holding the trade, a self-reinforcing dynamic layered on top of the buildup and the two initiating pieces of news.

August 5: the sharpest day. By the time markets in Asia opened on Monday, August 5, the combined pressure produced the sharpest single day of the episode. Japan's TOPIX fell 12 percent, its worst single-day performance in decades. The S&P 500 fell 3.0 percent that day, adding to a 1.8 percent decline from the prior Friday, and European stocks fell as well. The yen had appreciated by roughly 5.6 percent against the dollar over the six days from July 30 to August 5. The VIX spiked to an intraday level above 65 during the session, its highest reading since the early days of the COVID-19 pandemic in 2020, though still well below the levels reached during the 2008 and 2020 crises.

August 9: most of it reverses. Within four trading days, the S&P 500 had recovered all of the losses it incurred from that Monday, and Japan's TOPIX had recovered most of its own decline. The speed of that round trip suggests the initial move was substantially amplified by positioning and forced deleveraging rather than being a pure reflection of the underlying macro story. Subsequent US data and central-bank communication that came in more reassuring than feared also helped calm the growth concern behind the move. Both pieces matter: leveraged trades can reverse far faster than an economic outlook actually shifts, and the incoming data gave the market a reason to let them.

What made this episode specifically severe. The scale of the move wasn't just about the two pieces of news. Leveraged and volatility-sensitive strategies, including funds that mechanically reduce exposure as volatility rises, were estimated to have added forced selling on top of the initial repricing, the same kind of amplification mechanism that shows up across many sharp, short-lived market events, not something specific to carry trades or to Japan.

What this episode does and doesn't establish. It's a clean, well-documented illustration of a carry-trade unwind cascading through markets, and it's a useful case study precisely because two distinct, verifiable triggers arrived within days of each other. It doesn't establish that BOJ policy moves typically produce this scale of reaction, most BOJ decisions pass with far less drama, or that yen strength alone is a risk-off signal outside a similar setup. The scale here reflected a specific, multi-year buildup in carry positioning meeting two pieces of news at once, a combination that doesn't recur on a predictable schedule.