Trading activity rose across the board in September among the four large online brokers studied.

Daily average revenue trades, or DARTs, at TD Ameritrade Holding Corp. increased by 60,000 to 840,000 during September, while DARTs at Interactive Brokers Group Inc. rose by 66,000 to 807,000.

Total client assets increased at all but one of the five online brokerages that release monthly details.

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