Convertible Bonds and Hybrid Securities › Limitations and Impact

Convertible bonds and hybrid securities have changed how companies raise capital, but they have important limitations.

Accurate valuation is difficult. While our simple component model provides intuition, real valuation requires models that capture the interaction between credit risk and equity dynamics. When a stock price falls, credit quality typically deteriorates, meaning the bond floor erodes when needed most. This credit-equity correlation is difficult to model and can lead to unexpected losses. The 2008 financial crisis demonstrated this vividly when many "busted" convertibles (those trading well below par with the conversion option deeply out-of-the-money) experienced further declines as credit spreads widened.

The callable nature of most convertibles adds another layer of complexity. Issuers can typically call their convertibles when the stock rises significantly above the conversion price, forcing bondholders to convert and capping their upside. This call feature effectively transfers value from bondholders to the company, as the issuer exercises the call precisely when the embedded option is most valuable. Modeling callable convertibles requires assumptions about the issuer's call policy, adding uncertainty to valuation.

From a market impact perspective, convertible issuance and the associated arbitrage activity can create measurable effects on the underlying stock. When a company announces a convertible offering, the stock often declines as the market anticipates dilution. Convertible arbitrageurs who buy convertibles and short the stock create sustained selling pressure. These dynamics mean convertible issuance decisions have strategic implications beyond simple financing choices.

Despite these limitations, hybrid securities have enabled valuable financial innovation. They provide risk-sharing mechanisms that better align issuer and investor interests, allow companies to access capital markets at different stages of their development, and give you tools to construct portfolios with customized risk-return profiles. The principles underlying convertibles, combining debt protection with equity participation, appear throughout modern finance, from venture capital term sheets to complex structured products.