Momentum is a measure of how fats a stock price has increased. It is calculated by comparing the price of a stock today to the price of the same stock in the past, and then comparing that relation to those of other stocks. Research has shown that a portfolio of stocks that have performed the best over the past 6 months, versus all other stocks, will outperform the overall market over the next 6-12 months. This is why you want to include stocks that have performed well over the past 6 months into your portfolio.
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