It is important for the project manager to gather data on the work that has already been executed in the project to compare the plan against what is actually happening. Once the data is collected and reviewed, it should be determined if action is necessary. Without the data, project managers may not be able to make decisions based on how the project is progressing, more specifically, making sure the costs are within budget. By gathering data as work is executed, project managers can make decisions before the project is over and performance is presented to stakeholders.