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 Should I Invest In REITs? Are Real Estate Investment Trusts right for your portfolio? Global vs. International: What’s The Difference? International funds invest in non-U.S. markets, while global funds may invest in U.S. stocks alongside non-U.S. stocks. Keys to Investing for Retirement There are some key concepts to understand when investing for retirement.