As prices rise, a convertible tends to trade like a stock, its value moving in lock step with the underlying share price. Convertibles issued by companies whose stock prices are sinking tend to trade more like bonds, with prices driven more by movements in interest rates. The result is an "asymmetric" return profile, says Joe Wysocki, comanager of the Calamos Convertible fund, with convertibles effectively increasing investor exposure to stocks as they rally and limiting exposure when prices are falling.