where m0 and mt refer to the cash held by the subject at the beginning and the end of the trading period t. v0 and vt are the shares owned by the subject at the beginning and the end of that period, and Pt is the closing price. With this measure, if the subject was idle and did not engage in any trade, then m0 ¼ mt and v0 ¼ vt, and his end-of-period profit, pt, will simply be zero. If he did engage in transactions, pt can be positive and negative.