One of the most common measurements used by professional investors when they are comparing Forex funds track records is the standard deviation.  Standard deviation, in this case, is the level of volatility of returns measured in percentage terms over a period of many months or even years. The standard deviation of returns is a measurement that compares the variability of returns between funds when combined with data from annual returns.  Everything else being equal, an investor will deploy his capital in the investment with the lowest volatility.