TD Ameritrade Investor Movement Index: Big-Name Volatility Pushes IMX Score Higher in March By Staff 1 second ago An increase in relative volatility among widely held names, including Tesla Inc. (TSLA), Amazon Inc. (AMZN), and The Walt Disney Company (DIS) caused an increase in the IMX score during the March period ® (IMX SM) increased to 8.21 in March, up 8.74 percent from its February score of 7.55. The IMX is TD Ameritrade’s proprietary, behavior-based index, aggregating Main Street investor positions and activity to measure what investors actually were doing and how they were positioned in the markets. The reading for the four-week period ending March 31, 2021 ranks “High” compared to historic averages.