What it means
A single-name credit default swap covers one borrower, which is precise but slow to trade and expensive to assemble in bulk. An index bundles a set number of names, commonly 100 or 125 investment grade or high yield issuers, into one standardised contract with a fixed coupon and a set maturity.
That standardisation is what makes it liquid. The index is quoted as a spread in basis points, and that spread is effectively the market's price for corporate default risk.
When the quoted spread widens, protection has become more expensive because the market sees more danger; when it narrows, credit conditions are perceived as improving. Users fall into two camps.
Hedgers, such as a bank with a large corporate loan book, buy index protection to offset broad credit exposure they cannot hedge name by name, while traders use it to express directional views or to arbitrage against the underlying single-name contracts. Mechanically, the buyer pays a periodic premium and receives a payment if any constituent suffers a credit event.
Because each name is equally weighted, one default triggers a payout on only its share of the notional, after which that name drops out and the contract continues on a reduced notional. The important nuance is that an index hedge is a broad instrument, not a precise one.
If your actual exposure is concentrated in three borrowers and the index contains 125, the hedge will track your losses only loosely, a mismatch known as basis risk.
In practice
Real-world examples.
Example
A pension fund holding $400,000,000 of corporate bonds expects credit conditions to deteriorate but does not want to sell and crystallise trading costs. It buys $150,000,000 of index protection, which rises in value as spreads widen, offsetting part of the mark-to-market fall in the bond portfolio.
Example
A bank's treasury team uses the high yield index level as a daily market read on credit sentiment. When the index widens from 340 to 520 basis points over three weeks, the team tightens internal lending limits before any borrower has actually missed a payment.
Example
A hedge fund believes the index is trading wider than the sum of its individual constituents warrants. It sells index protection and buys single-name protection on the constituents, aiming to capture the difference between the two prices.
Formula
Calculation
Annual Premium = Notional x Index Spread
Default Payout = (Notional / Number of Constituents) x (1 - Recovery Rate)
A credit fund buys $100,000,000 of protection on a 125-name investment grade index quoted at 100 basis points, which is 1%. The annual premium is $100,000,000 x 0.01 = $1,000,000, paid quarterly at $250,000.
One constituent then defaults. Each name carries an equal weight of 1 / 125 = 0.8%, so the defaulted name represents $100,000,000 x 0.008 = $800,000 of notional. The post-default auction sets recovery at 40%, so the fund receives $800,000 x (1 - 0.40) = $480,000.
The defaulted name is then removed and the contract continues on a reduced notional of $100,000,000 - $800,000 = $99,200,000, cutting the annual premium to $99,200,000 x 0.01 = $992,000.Case study
Seen in the real world.
Ashgrove Capital is an invented asset manager used purely as an illustrative example. It held $250,000,000 of investment grade corporate bonds and expected a difficult credit quarter, so it bought $80,000,000 of index protection at 90 basis points, costing $80,000,000 x 0.009 = $720,000 a year.
Spreads did widen, from 90 to 160 basis points, and the protection position gained roughly $2,400,000 in mark-to-market value while the bond portfolio lost about $4,100,000. The hedge recovered a little under 60% of the loss, which was the point: the index and the portfolio were not identical, so the offset was partial by design.
The illustrative takeaway is that an index hedge buys broad, liquid, imperfect cover. Ashgrove's committee accepted the residual basis risk knowingly rather than discovering it afterwards.
Watch out
Common mistakes.
- Treating an index hedge as an exact offset. The index covers its own constituents at equal weights, so it will rarely match a real portfolio's concentrations.
- Assuming a default wipes out the whole notional. Only the defaulted name's share pays out, and the contract continues on the reduced remainder.
- Reading the quoted spread as a default probability. Spread also compensates for liquidity, risk appetite and recovery uncertainty, so it consistently overstates pure default odds.
Questions
People also ask.
How are constituents chosen?
Index providers select the most liquid issuers meeting the rating and sector rules, and the list is refreshed on a fixed schedule, typically twice a year.
Who can trade these contracts?
They are over-the-counter instruments traded between institutional participants, usually cleared through a central counterparty, and are not available to retail investors.
What happens at each index roll?
A new series is launched with an updated constituent list, and liquidity migrates to it, so hedgers who want to maintain cover must roll their positions across.
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