Quote from cherubian:
...but for the year I analyzed, the upward movement came from overnights, and between the open and the close the market was actually quite negative on the year.
This is a plain old missunderstanding of the concept of movement. As I said, only unfilled gaps classify as overnight movements, any gap filled during the day means that the actual move also happened intraday.
Example: SPX opens with a 20 points upgap, but then drops back and fills it 75%, before continuing the rally. So how much movement was achieved overnight really? A whole 5 points!!! 3/4 of the movement was also and eventually done intraday! (and I don't even bring up the subject of gaps filled a few days/weeks later)
Last year the SPX dropped 560 or so points. I bet there is no more than 25 points gap left behind which is below the 5%, what I stated in my previous post....