TDAmeritrade's IMX Index Saw Its Second Largest Drop Since December 2012

TD Ameritrade created a monthly index called the "Investor Movement Index" (IMX), a behavior-based index designed to indicate the sentiment of retail investors. The index "measures what investors are actually doing, and how they are actually positioned in the market."

If the index rises month-over-month, it likely implies investors are becoming more bullish. Data are randomly collected from a monthly sample of retail clients who have placed trades in a given month.

The index plunged 9.16 percent to 4.76 in September, marking the second-largest monthly decline since the index was created in December 2012.

"As we saw in August, many of the widely held positions within TD Ameritrade client accounts saw decreases in their volatility relative to the market, which pushed the IMX lower," the company stated. "TD Ameritrade clients were also net buyers for the month of September, which typically would work to increase the IMX reading; however, this month we saw volatility in many of those companies decrease at a faster rate than that of the overall market."

Net Buyers In September

TD Ameritrade continued that Apple Inc. (NASDAQ: AAPL) was a "popular" net buyer in September, as were high-yielding divided players Exxon Mobil Corporation (NYSE: XOM) and Chevron Corporation (NYSE: CVX). Investors were also net buyers of Verizon Communications Inc. (NYSE: VZ) following the announcement of its streaming video service.

Additionally, investors were net buyers of GoPro Inc (NASDAQ: GPRO), as it traded lower toward IPO price.