Research into factor strategies has generated a large number of additional factors in recent years. The most widely used factors today are value, quality, momentum, low volatility and size. The definition of factors varies significantly between different economists and providers. Many providers continue to orientate themselves on the classic factor definitions of Fama-French or other economists who mainly wrote their studies in the 1990s.
However, the following chart shows that the two classic factors of size (company size) and value (price-to-book ratio) according to the Fama-French definition have no longer been delivering excess returns for some years.