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 Global and International Funds Investors seeking world investments can choose between global and international funds. What's the difference? Four Really Good Reasons to Invest There are four very good reasons to start investing. Do you know what they are? Keys to Investing for Retirement There are some key concepts to understand when investing for retirement.