The study was done from 1993 to April 2010 so it covered both bull and bear markets 'collectively'. I would have liked to see a breakdown myself using previous bull and bear market results to compare. It might not be relevant overall but would be nice to know ahead of time. But as long as you keep in mind the amateurs opening the prices and professionals closing them that should be a good guide. I have read that many professional traders use the end of day price relative to the day's price action to tell them what the short term trend is and trade in that direction as that is what the professionals are doing with their portfolios. So if price sells off on the close the pros are exiting their positions which is bearish. And visa/versa.