After sitting out most of the nearly nine-year bull market, individual investors are finally pouring in.

Discount brokerages TD Ameritrade Holdings Corp., E*Trade Financial Corp. and Charles Schwab Corp. reported surges in client activity at the end of 2017 that have accelerated in January. The firms attributed much of the activity to retail, or individual, investors who are opening brokerage accounts for the first time, some of them lured by the boom in cryptocurrency and cannabis investments.

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