For all the trepidation over a Trump administration, retail investors stayed squarely on the bullish side to start the year.

The behavior-based TD Ameritrade Investor Movement Index, or IMX, which aggregates Main Street investor positions, rose 4.2%, to 5.71 in January, as retail investors increased their exposure to the U.S. equity markets to start the new year. The S&P 500 rose 1.8% for the month, while the VIX, or so-called fear index, fell from 14 to 12.

"January started like gangbusters and the retail client was right there having exposure to the market," said JJ Kinahan, chief strategist at TD Ameritrade (AMTD) - Get Report .

Each month, TD Ameritrade pulls a sample from its client base of 6 million funded accounts that includes all accounts that completed a trade in the past month. The holdings and positions of this statistically significant sample are evaluated to calculate individual scores, and the median of those scores represents the monthly IMX.

TD Ameritrade clients were net buyers of banks in January, notably JP Morgan Chase (JPM) - Get Report and Bank of America (BAC) - Get Report , which are both expected to benefit from rising interest rates and a rollback in regulations. Nvidia (NVDA) - Get Report was a net buy for the second month in a row as shares appeared to stabilize following a volatile December.

Teva Pharmaceuticals (TEVA) - Get Report and Dry Ships (DRYS) - Get Report were also net buys; both have seen recent volatility. Net buying continued in Amazon (AMZN) - Get Report as well.

Apple (AAP) - Get Report , on the other hand, was net sold as the stock reached a new 52-week high.

"People are taking an opportunity when these stocks go up to lighten up their positions," says Kinahan. "Plus I think the sexiness factor surrounding Apple is not quite what it once was. People don't wait on line for three or four hours anymore like they were at one point."

Tesla Motors (TSLA) - Get Report and Alcoa (AA) - Get Report were also net sold as their share prices posted significant increases during the period.

Finally, Walt Disney (DIS) - Get Report and Yahoo! (YHOO) were net sold as each reached new year-to-date highs in January. Chipotle Mexican Grill (CMG) - Get Report and Alibaba Group (BABA) - Get Report were both net sold following share price increases after volatility over the past few months.

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