“A factor can be thought of as any characteristic relating a group of securities that is important in explaining their return and risk. A large body of academic research highlights that long term equity portfolio performance can be explained by factors. This research has been prevalent for over 40 years; Barra (now an MSCI company) for instance has undertaken the research of factors since the 1970s.
Certain factors have historically earned a long-term risk premium and represent exposure to systematic sources of risk. Factor investing is the investment process that aims to harvest these risk premia through exposure to factors. We currently identify six equity risk premia factors: Value, Low Size, Low Volatility, High Yield, Quality and Momentum. They are grounded in academic research and have solid explanations as to why they historically have provided a premium.”
To learn more: Foundations of Factor Investing