我自己的答案,谢谢!
1. 可用style analysis来确定benckmark.用previous return来找style return,可作为benckmark。用return/variability可以来评价。如果slection/standard deviation of selection > style/starndard deviation of style,即beat the benchmark on risk-adjusted basis.
2.Active managers can attempt to add value through various channels including market timing, market choice, security selection, currency selection. If he does, some other underperformers including other fund managers, individual investrors may lose. It contribute to market efficiency cause the way these fund managers looking for and investing on undervalued or overvalued stocks accelerate the stocks moving towards their intrinsict values.