I think that the risk/benefit ratio is something that is looked at throughout the entire project and it is something that is consistently changing as the project moves along. As every action will carry a risk/benefit ratio it is important to look at how one ratio can affect a ratio later on. It is also means that different risk and benefits are weighed differently. You have to combine all the risks and benefits together to get an accurate ratio and can not just analyze one or two aspects of the project. Ideally you want the ratio to be as close to zero as possible so that your benefits will greatly outweigh the risks. By constantly analyzing the risk/benefit ratio you can see how the project is changing over time and you can possibly identify trends as to how the ratio will continue to change based on how the project is going and what is next to be done.