Dollar Funding Squeezes and Basis Blowouts

The world outside the United States runs on dollars far more than the size of America's own economy would suggest — trade is invoiced in dollars, companies borrow dollars, banks fund dollar loan books. Almost none of those dollars come from a US bank branch abroad; they are borrowed synthetically, mostly through the FX swap market. That machinery works fine in calm times. In a crisis, when every non-US bank suddenly wants more dollars at once and US money-market funds simultaneously pull back from lending, the price of borrowing dollars this way spikes far above what US interest rates alone would suggest — a dollar funding squeeze.

Why the squeeze concentrates in the basis

Recall that an FX swap's implied yield should, in theory, roughly match each currency's own money-market rate — that is what covered interest parity predicts. The gap between the implied rate and the real rate is the cross-currency basis, and it is normally small. It stops being small when the banks that normally act as the bridge between the two markets — arbitraging away exactly that gap — pull back because their own balance sheets are constrained, at year-end regulatory reporting dates, or because they are worried about counterparty risk during a crisis. With fewer arbitrageurs willing to supply dollars through the swap market, non-US borrowers bid the implied dollar rate up sharply, even while the actual Fed funds rate has not moved at all.

Worked example

In calm markets, borrowing dollars synthetically through a 3-month euro/dollar FX swap might imply a rate of 4.85% against an actual US 3-month rate of 4.80% — a basis of about -5 basis points, small and unremarkable. During an acute funding squeeze, that implied rate can jump to 5.60% or higher against an unchanged 4.80% US rate, a basis of -80 basis points or worse. A European bank funding a $500 million dollar loan book through the swap market would see its funding cost jump by roughly 0.75 percentage points overnight, purely from the squeeze, with no change in the underlying US rate at all.

What this means in practice

Central banks watch the basis as a real-time stress gauge and have a standing tool to relieve it: dollar swap lines between the Federal Reserve and other major central banks, which let a foreign central bank borrow dollars directly from the Fed and re-lend them to its own banks, bypassing the clogged private swap market entirely. Announcements or expansions of these swap lines are themselves read by markets as a signal of how seriously policymakers are taking the squeeze.