The term "beta" was first introduced by Nobel Laureate William Sharpe in the 1960s. In simple terms, it denotes the risk of the stock market. But in the intervening half a century, several other risk factors have been identified and quantified. The third part of our series explores these developments, with contributions from Garrett Quigley and Bernd Hanke of Global Systematic Investors, whose model increases diversification in a cap-weighted portfolio to somooth out the highs and lows.