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 What Smart Investors Know Smart investors take the time to separate emotion from fact. Best Performing Asset Classes Bonds may outperform stocks one year only to have stocks rebound the next. 5 Smart Investing Principles Principles that can help create a portfolio designed to pursue investment goals.