Convertible bond
From Wikipedia, the free encyclopedia
A convertible bond is a type of bond that can be converted into shares of stock in the issuing company, usually at some pre-announced ratio. Although it typically has a low coupon rate, the holder is compensated with the ability to convert the bond to common stock, usually at a substantial premium to the stock's market value.
Other convertible securities include exchangeable bonds, where the stock underlying the bond is different from that of the issuer; convertible preferred stock, which is similar in valuation to a bond, but with lower seniority in the capital structure; and mandatory convertible securities, which are short duration securities---generally with high yields---that are mandatorily convertible upon maturity into a variable number of common shares based on the stock price at maturity.
From the issuer's perspective, the key benefit of raising money by selling convertible bonds is a reduced cash interest payment. However, in exchange for the benefit of reduced interest payments, the value of shareholder's equity is reduced due to the dilution expected when bondholders convert their bonds into new shares.
From a valuation perspective, a convertible bond consists of two assets: a bond and a warrant. Valuing a convertible requires an assumption of 1) the underlying stock volatility to value the option and 2) the credit spread for the fixed income portion that takes into account the firm's credit profile and the ranking of the convertible within the capital structure. Using the market price of the convertible, one can determine the implied volatility (using the assumed spread) or implied spread (using the assumed volatility).
This volatility/credit dichotomy is the standard practice for valuing convertibles. What makes convertibles so interesting is that, except in the case of exchangeables (see above), one cannot entirely separate the volatility from the credit. Higher volatility (a good thing) tends to accompany weaker credit (bad). The true artists of convertibles are the people who know how to play this balancing act.
A simple method for calculating the value of a convertible involves calculating the present value of future interest and principal payments at the cost of debt and adds the present value of the warrant. However, this method ignores certain market realities including stochastic interest rates and credit spreads, and does not take into account popular convertible features such as issuer calls, investor puts, and conversion rate resets. The most popular models for valuing convertibles with these features are finite difference models such as binomial and trinomial trees.
