 OMAHA, Neb.--BUSINESS WIRE--The Investor Movement Index IMXSM increased to 6.26 in December, up 15.71 percent from its November score of 5.41. The IMX is TD Ameritrades 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 December 24, 2020 ranks Middle compared to historic averages. To cap off a tumultuous year, the 