TD Ameritrade has started to offer individual investors around-the-clock weekday trading for some popular funds. The company said one driver for the change is Asian clients who want to trade U.S. stocks during their daytime hours. The company also wants to satisfy U.S. clients who want to trade in off hours. Analysts point out that constant trading isn’t the best portfolio strategy, and that Ameritrade stands to make money on more frequent trades.

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