Indexes are weighted by their size, primarily market cap. Research Affiliates’ latest index focuses on Growth, rejiggering these indexes based on how fast companies are growing. At The Money', Barry speaks with Rob Arnott, founder of Research Affiliates (RAFI). Each week, “At the Money” discusses an important topic in money management. From portfolio construction to taxes and cutting down on fees, join Barry Ritholtz to learn the best ways to put your money to work.