The current literature or business finance states that debt is a cheaper source of capital than stock (tending to reduce the firm's cost of capital), because interest is deductible for income tax purposes while the return to common stockholders is subject to tax. It is even possible to issue debt without increasing the risk to the owners (the debt is issued to stockholders in proportion to the ownership of stock, or equivalently investors buy a mixture of stocks and bonds on the market). However, it is argued in this paper that if we assume that the present stockholders have no further resources available for investment in the firm, but the enterprise needs additional resources, then the present stockholders have to make a basic decision about whether to issue stock or debt to raise the additional needed capital. The issuance of debt in this situation increases risk, and the issuance of stock dilutes ownership. Even when bondholders require a much lower contractual return than the expected annual return of stockholders, the issuance of more stock may be preferred to the issuance of debt.

Victor L. Bernard, Thomas J. Frecka, Commodity Contracts and Common Stocks as Hedges against Relative Consumer Price Risk, The Journal of Financial and Quantitative Analysis, Vol. 22, No. 2 (Jun., 1987), pp. 169-188

We examine market efficiency before and after the 1987 Market Crash using the box spread strategy implemented with European-style S&P 500 Index (SPX) options. Before the Crash, apparent arbitrage opportunities were rare and simulated trades were unprofitable assuming a one-minute execution delay. After the Crash, apparent arbitrage opportunities were frequent and simulated trades were profitable even assuming a five-minute execution delay. Our analysis makes the routine assumption that quotes are good until updated to construct a time series of prevailing quotes sampled at 30-second intervals. If this assumption is valid, then arbitrage profits were actually available. If this assumption is invalid, then such profits could have been illusory. Either scenario, however, implies that SPX market efficiency decreased following the Crash—prevailing price quotes repeatedly failed to satisfy the fundamental parity relation underlying the box spread.

We test whether the conversion price (ratio) is viewed by the stock market as a credible signal of the firm's future earnings prospects (Kim (1990)) and, subsequently, whether convertible debt serves as backdoor equity financing (Stein (1992)). Examining the conversion price in relation to current stock prices and a priori growth expectations produces an average expected time of less than 1.5 years for convertible bonds to be at-the-money. Thus, as Stein suggests, convertibles appear to be a method of drawing equity into a firm's capital structure. We also find that the size of the firm's announcement period abnormal returns is positively related to the expected time for the convertible to become at-the-money. Given these relationships, we conclude that convertible debt issue announcements, on average, send an equity-like signal to the market.