They were able to get a fit like:
mfp = A/E^2 + Bsqrt(E), where E is the initial electron kinetic energy
If we add up the mfp for each value E as it drops, it becomes an integration effectively, and it is pretty clear the inverse power dominates. So actually the "zero energy" electron determines the overall path length. They also stick around the longest (since they are slowest electrons) and hence are most chemically active.