Why Short-Term Funding Pressure Shows Up in FX Swaps

Start with the simplest money market there is

Imagine you need cash for one night and you have a government bond in your pocket. You hand the bond over, take the cash, and agree to buy the bond back tomorrow at a slightly higher price. That is a repurchase agreement, or repo. Economically it is a short-term loan with collateral attached, and the small difference between the selling price and the repurchase price is the interest rate, called the repo rate.

One number in that arrangement does most of the quiet work. Lenders rarely hand over the full value of the bond. They hold back a slice, so if the borrower vanishes they still have a cushion when they sell the collateral. That slice is the haircut. A two percent haircut on a US Treasury trade means you post collateral worth a bit more than the cash you receive. Simple, sensible, and the foundation for everything below.

Where the warehouse sits

Most overnight repo involving US government securities runs through a tri-party structure. Two parties negotiate the trade, but a third party, the clearing bank, handles collateral valuation, margining and settlement on its books. As of 2019 the Bank of New York Mellon was the only provider of this service in the US tri-party repo market, and overnight trades make up roughly 80 percent of daily traded volume there.

This warehouse function matters because it lets cash lenders participate without physically holding securities. It also means collateral is allocated automatically from a borrower's inventory against a pre-agreed schedule. For the reader keeping score: the plumbing is invisible, until it isn't.

Haircuts are not decoration

Haircuts vary enormously by collateral type. Treasury haircuts in the tri-party market have long clustered around 2 percent with little variation. That uniformity is partly convenience. Money market funds, big cash lenders in this market, often prefer a simple standard over finely tuned, trade-by-trade risk pricing.

But outside the tri-party world, haircuts look very different. In the non-centrally cleared bilateral market, where dealers largely borrow from hedge funds against specific securities, a large share of Treasury trades carry no haircut at all, and some carry negative haircuts. Negative sounds strange until you remember who needs protecting. If a hedge fund is lending cash to a dealer purely to obtain a specific bond, the dealer is the one exposed to losing valuable collateral. The haircut can flip direction.

So the same phrase, "Treasury repo haircut," covers numbers that are not comparable. Comparing a 2 percent tri-party haircut with a bilateral trade is a bit like comparing the price of a hotel room with the price of the building.

Collateral substitution and the timing game

Collateral is not just a risk buffer. It is a signal. Federal Reserve research on the overnight tri-party market shows that riskier, less liquid collateral tends to get arranged earlier in the day, because fewer counterparties will accept it and borrowers want time to find a home for it. Higher-quality collateral is easier to place and can wait.

When funding is comfortable, borrowers may substitute collateral almost casually, swapping Treasuries for agency securities or other assets as their inventory shifts. When funding tightens, that substitution becomes expensive. Lenders narrow the list of what they will accept, haircuts on lower-quality collateral rise, and borrowers who planned to roll a trade with something other than Treasuries discover the door has narrowed. Relationship history starts to matter more than the rate sheet, because only counterparties who previously signed a master agreement covering that collateral type can trade with you at all.

Research on this market finds that participants with more trading relationships tend to get more favourable rates and haircuts. Connections, in other words, are priced.

How this reaches an FX swap

Now the interesting leap. An FX swap is a transaction where two parties exchange currencies at the spot rate today and agree to reverse that exchange at a forward rate later. Functionally, you borrow one currency and lend another for a set period. The cost of doing so should, in theory, line up precisely with the interest rate difference between the two currencies. That tidy relationship is called covered interest parity, and it has been violated persistently since the global financial crisis.

The violation appears as a cross-currency basis: the gap between borrowing a currency by swapping into it and borrowing it directly in cash markets. For most currencies against the dollar, that basis has been negative, meaning borrowing dollars through the swap market became more expensive than direct dollar funding.

Two forces explain it. First, there is a large, largely price-insensitive demand for dollar hedges from banks managing balance sheet mismatches, insurers and pension funds hedging foreign assets, and companies that issued debt in one currency and want another. Second, the arbitrageurs who would normally close the gap face limits. Balance sheet space costs money. Capital rules, leverage ratios and counterparty risk management all mean that taking the other side of hedging demand is not free.

Here is the bridge back to repo. For hedge funds in particular, the funding and availability of repo market collateral is central to running that arbitrage. If repo haircuts rise, or acceptable collateral narrows, the arbitrageur needs more cash for the same position. It becomes more expensive to intermediate, and the basis can widen rather than close. Short-term funding pressure does not stay in the funding market. It seeps outward.

The same logic runs through broker credit lines. Dealers who intermediate both repo and FX swaps are managing one balance sheet. When haircuts rise and collateral becomes harder to finance, the cost of extending credit to clients rises with it, and lines get repriced or rationed. Repo stress and swap pricing are often described as separate topics. In a dealer's risk system they are frequently the same conversation with the same spreadsheet.

Where uncertainty lives

A few honest caveats. The exact transmission between repo conditions and FX swap pricing depends on the arbitrageur, the currency pair and the regulatory regime, and it varies by jurisdiction. US repo market structure, European bank constraints and Japanese hedging flows are not interchangeable. Data coverage is also uneven: regulators still do not collect comprehensive data on all types of repo, which is precisely why official statistics and central bank research notes exist.

Haircut practices have also changed over time. Low or zero haircuts in some Treasury repo segments have raised questions among researchers about whether margining is sufficiently risk-sensitive, while others point out that minimum haircuts applied bluntly could reduce liquidity without improving protection. That debate is live, not settled.

What to hold on to

The chain is longer than most headlines suggest. A haircut negotiated in an over-the-counter trade determines how much cash a borrower must find. How much cash they must find shapes the cost of intermediating positions. That cost shows up in the price of swapping one currency for another, and in the terms on a broker's credit line.

None of this tells you what any market will do next. It does explain why a quiet adjustment in collateral terms can travel further than the trade it was written for, and why the people who watch these numbers treat a two percent haircut as a data point rather than a formality. Finance, it turns out, is mostly plumbing with better branding.