Abstract
We examine how the presence of fast traders impacts price discovery and efficiency in a real-world setting, i.e., courtsiding, the activity of live betting from a tennis stadium. This setting allows us to isolate the activity of fast-acting traders who have a short-term monopolistic access to important information with respect to other traders who trade based on delayed TV images. Using live-tennis betting data combined with detailed point-by-point match data, our results show that courtsider trading promotes quick price discovery and correctly incorporates new information into prices. We estimate that a simple trading strategy yields a positive trading return to fast traders after the occurrence of important informational events.