Weighted Alpha is a measure of how much a stock has risen or fallen over a one-year period. The original research was restricted to large cap stocks, so the corresponding rise in the S&P 500 index was subtracted; however, as there are a number of interesting stocks that do not fit well into any category, and others that fit into more than one category, the results are presented without subtracting any index.
Barchart.com takes this alpha (measure of how much a stock has changed in the one-year period) and weights this, assigning more weight to recent activity, and less (0.5 factor) to activity at the beginning of the period. Thus the weighted alpha is a measure of one year growth with an emphasis on the most recent price activity.
A stock whose price has risen over the one-year period will have a positive Weighted Alpha. A stock whose price has not changed in the period will have a small Weighted Alpha and a stock whose price has dropped over the period will have a negative Weighted Alpha.
Note: The Weighted Alpha is limited in the amount it may change from one day to the next, thus eliminating large price jumps from the calculation.