I was going to suggest that the closest would be a logical reason, but that is somewhat misleading as this may diminish ever so slightly at the extremes. As for the most liquidity - in terms of stops - while off subject, also explains why stocks tend to be more volatile on an intra-day basis when between two short-term moving averages (on the daily chart). Because a market will often test and re-test both intra-day. The stats become much more informative, the more you test the data. This is because there are 'Sweet Spots' (Ranges) where the stats say historically it would be to one's advantage to be either long or short. These findings came as a surprise and opened my eyes to see that something that I believed was not true, actually is. While I had designed a few strategies to take advantage of what was happening (although I did not believe the concept), I did not understand why they were profitable. This type of research actually demonstrated the reason and validated the concept.