Investors measure success by looking at the rate of return on their investments. This is as it should be. Those who actively manage their portfolios are often looking for an edge, a winning formula that will help them outperform a peer group or a benchmark. They seek out companies that are poised to take off, mutual funds with five-star ratings and asset managers with the best track records. But most of them miss a huge opportunity to boost portfolio returns; one that is easy to implement and proven to deliver significant long-term benefits. With so much focus on picking securities and timing the market, they fail to properly manage the cost of their investments.