In automated negotiation systems consisting of self-interested agents, contracts have traditionally been binding, i.e., impossible to breach. Such contracts do not allow the agents to act efficiently upon future events. A leveled commitment protocol allows the agents to decommit from contracts by paying a monetary penalty to the contracting partner. The efficiency of such protocols depends heavily on how the penalties are decided.In this paper, different leveled commitment protocols and their parameterizations are empirically compared to each other and to several full commitment protocols. Many different aspects of contracting are studied, such associal welfare achieved, CPU-time usage, and amount of contracting and decommitting.If a global clock is used for increasing the decommitment penalties, infinite decommitment loops are prevented, while a local clock cannot guarantee this. Concerning solution quality, the leveled commitment protocols are significantly better than the full commitment protocols of the same type, but the differences between the different leveled commitment protocols are minor.