This is the distribution of (total time)/(2*halfway-time). If you run a flat pace, this number comes out one. People that are ill-prepared for the marathon would score well above one, as they typically crash in the second half of the race. The blue line is for all participants, the yellow line for the Dutch. Notice: they are nearly the same! As it turns out, 27.1% of the Dutch runs a negative split (value smaller than one) versus 28% of all runners. Average Dutch time is 4:28:06, versus 4:36:46 for the entire field.