The Omaha-based online brokerage says its recently created Investor Movement Index registered 4.71 on the six-point scale in January.
Ameritrade's Steve Quirk says the index shows investors buying in January, but they were less aggressive than December when the index hit 4.94.
The index is based on what TD Ameritrade Holding Corp.'s 6 million clients were buying and selling. Inactive accounts are excluded.
Ameritrade says its investors were buying stock in Apple, Facebook, 3D Systems, Microsoft and AT&T stock in January. They sold shares of Dell, Citigroup, JP Morgan Chase and Halliburton as those stocks hit the highest point in recent months.
TD Ameritrade investor index: www.tdameritrade.com/IMX