Provide liquidity, improve efficiency. 他们一直存在,说明他们是能赚钱的。
只要你有时间精力,就可以做。要心里要有数你的信息不足,市场上有大的institutional investors, 他们信息比你充足,有时是zero sum game
还有,frequent trading has tax consequences, it is always the after tax return that matters. 交完capital gain tax 以后,你的return 是多少?还要想到这点