In this white paper we introduce Momentum, one of the Systematic Equity Strategy (SES) factors modeled by MSCI Equity Analytics Research.  This paper finds that the SES Momentum factor measures the tendency of equities that have outperformed the market to continue outperforming while underperformers keep underperforming. The persistence of this factor is well documented, and so are the periodic, sharp reversals at market inflection points. Behavioral finance theory supports these...