Cross-currency Basis and Funding Cost

What this topic is

Covered interest parity says that borrowing dollars directly and borrowing another currency then swapping it into dollars must cost the same, because otherwise there is a riskless arbitrage. Since 2008 that relationship has broken persistently. The gap is called the cross-currency basis, and it is quoted as a spread added to the non-dollar leg of a cross-currency basis swap. A negative basis means dollars obtained through the swap market cost more than dollars borrowed directly - the whole reason the number exists.

Why it matters

The basis is a direct, observable price on the cost of dollar funding for anyone who does not have natural dollar deposits. It determines whether a European insurer can profitably own US corporate bonds, whether a US company can issue cheaply in euros, whether a Japanese bank can fund its dollar loan book, and what a central bank swap line has to be priced at to be useful. It also quietly destroys apparent arbitrages: a foreign bond that looks 40 basis points cheap can be 15 basis points expensive once the basis is paid.

Who should learn it

Treasurers deciding where to issue, fixed income investors evaluating hedged foreign assets, bank funding and asset-liability management teams, and anyone who needs to understand why a parity condition taught as an identity is violated every day.

What you will understand

• How to compute a hedged yield in either direction and which side of the swap pays the basis
• Why the arbitrage that should close the gap does not, and what changed in bank regulation to make that true
• What moves the basis: hedging demand, issuance flows, reporting dates, and central bank swap lines
• How the basis is handled in hedge accounting under both US and international standards

Prerequisites

• Covenant Headroom Modelling
• Total Return Swaps as Financing

Common misconception

The cross-currency basis is often described as a market inefficiency, or as evidence that arbitrageurs are asleep. It is neither. The arbitrage is real and it is visible to everyone, but executing it consumes a dealer's balance sheet, and since the Basel III leverage ratio, balance sheet is a scarce priced resource rather than a free one. The basis is therefore not a mispricing - it is the rental price of the balance sheet needed to close it. That reframing matters practically: it tells you the basis will be widest when balance sheet is scarcest, which is quarter-ends, year-ends, and crises, and that it will not converge to zero simply because someone points out that it should.