The price of anarchy (PoA) has been widely used in static games to quantify the loss of efficiency due to noncooperation. Here, we extend this concept to a general differential games framework. In addition, we introduce the price of information (PoI) to compare game performances under different information structures. We further characterize these two relative measures of performance for a class of scalar linear quadratic differential games. We obtain bounds on the PoI and the PoA for feedback differential games. We also find their approximations in a large population regime.