This paper examines the effect of debt and liquidity on corporate investment in a continuous-time framework. We show that stockholder–bondholder agency conflicts cause investment thresholds to be U-shaped in leverage and decreasing in liquidity. In the absence of tax effects, we derive the optimal level of liquid funds that eliminates agency costs by implementing the first-best investment policy for a given capital structure. In a second step we generalize the framework by introducing a tax advantage of debt, and we show that an interior solution for liquidity and capital structure optimally trades off tax benefits and agency costs of debt.

Our main goal is to investigate the question of which interest‐rate options valuation models are better suited to support the management of interest‐rate risk. We use the German market to test seven spot‐rate and forward‐rate models with one and two factors for interest‐rate warrants for the period from 1990 to 1993. We identify a one‐factor forward‐rate model and two spot‐rate models with two factors that are not significantly outperformed by any of the other four models. Further rankings are possible if additional criteria are applied.