Convertible Arbitrage
Convertible Arbitrage is a market-neutral hedge fund strategy that purchases convertible bonds — debt instruments with embedded equity conversion options — while simultaneously shorting the underlying common stock, aiming to profit from mispricing between the convertible and the equity it represents while hedging out directional market exposure.
A convertible bond is a hybrid security: it pays a fixed coupon like a conventional bond but also grants the holder the right to convert the bond into a specified number of shares of common stock. This optionality makes convertibles intrinsically more complex to value than either pure debt or pure equity. Convertible arbitrageurs attempt to exploit situations where the market prices the convertible inconsistently with the implied value of its component parts.
The strategy's foundation is the delta hedge. The convertible's equity sensitivity — its delta — is estimated using option pricing models, and a corresponding short position in the underlying stock is established to neutralize first-order equity exposure. If the stock falls, the short position gains, partially offsetting the decline in the convertible's equity value. If the stock rises, the conversion option gains value faster than the short position loses, generating a positive gamma return. The convertible also generates coupon income, while the stock short position may generate rebate income from securities lending.
Profits arise from several sources. Volatility capture (or gamma trading) generates returns as the portfolio is continuously rebalanced: when the stock falls, the delta decreases and the arbitrageur buys back some shares; when the stock rises, additional shares are sold short. This systematic buy-low-sell-high rebalancing profits from realized volatility. Additionally, if the convertible is priced cheaply relative to its theoretical fair value — often measured as implied volatility below what the arbitrageur believes is fair — the strategy earns from that mispricing as it corrects.
The strategy carries several risks. Credit risk exists because a deteriorating issuer can cause the bond floor to decline sharply. Liquidity risk is significant — convertibles trade over-the-counter with wider bid-ask spreads than common stocks, and in periods of stress, convertible prices can gap sharply. Short squeeze risk arises when the borrowed stock becomes difficult to maintain. And correlation risk emerges when convertible implied volatility collapses at the same time credit spreads widen — exactly the dynamic that crushed many convertible arb funds in 2008.
Converter arb is naturally capacity-constrained because the convertible bond market is relatively small (roughly $300 to $400 billion in US issuance at any given time) and issuance tends to surge during bull markets when companies exploit low borrowing costs. The strategy has historically thrived in periods of moderate volatility with stable credit conditions, and has underperformed during volatility collapses (squeezing gamma profits) or severe credit stress (widening bond floors).