The Rule of 72 Do you know how long it may take for your investments to double in value? The Rule of 72 is a quick way to figure it out. Share | Related Content It Was the Best of Times, It Was the Worst of Times All about how missing the best market days (or the worst!) might affect your portfolio. How the Federal Reserve Works Each day, the Fed is behind the scenes supporting the economy and providing services to the U.S. financial system. Keys to Investing for Retirement There are some key concepts to understand when investing for retirement.