Two trillion dollars, rolled every morning
The long end has been selling off for a week; the largest single holder of the bonds being sold is a set of funds that finance them overnight and are sized by leverage rather than conviction.
The Office of Financial Research published a blog post on 19 August putting hedge funds' cash Treasury holdings at roughly $2 trillion, against about $1.4 trillion of short Treasury futures. Its own explanation of how the position is funded is worth reading slowly: because the profit on each unit of the cash-futures basis trade is tiny, "hedge funds scale positions by relying heavily on leverage through repo financing and futures margining", and they "typically rely on overnight repo because it is cheaper than term financing". So the mechanism is this. A fund buys a Treasury bond, sells the matching future, and pledges the bond in repo to borrow almost its full value back. The borrowed cash buys more bonds. The collateral is rehypothecated down a chain. The whole structure earns a few basis points and is rolled every single morning. It works until either repo rates spike or the futures exchange raises initial margin — at which point the fund does not choose whether to sell. Two supporting numbers matter. The July FOMC minutes, released the same day, described leverage vulnerabilities as "notable" and said hedge fund leverage was near all-time highs across all strategies and concentrated in the largest funds. And Fed work on Form PF data puts the basis trade itself at roughly $830bn and swap-spread arbitrage at about $305bn as of September 2025. The SEC's Treasury clearing rule took effect in May 2026 and was meant to put more of this through a central counterparty. Per a second OFR post, affiliate repo transactions are exempt where the affiliate clears its other eligible repos, and FICC does not clear open-term repo at all, so that stays outside too. The rule captures less than the headline suggests.