This chart shows the representative speeds at each of the measuring points across the race. By showing the 10 evenly spaced results across all the runners, the spread of speed across all the runners is made visible. 80% of all the finishers are in a very tight band. The fastest speeds and slowest speeds are quite separated from the mass of the population. From 1970-1999, runners were measured from the time the gun went off to the time they crossed the finish line. Note that there is some inaccuracy, as it takes a while for the crowd to get to the start line. From 2000-2005, runners were tracked with an electronic tag at the start, 10KM, midpoint, and end. From 2006 on, they are timed at every 5km as well as the halfway point and the end. The data is very imperfect, but every attempt has been made to correct errors.