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. A Primer on Dividends A company's profits can be reinvested or paid out to the company’s shareholders as “dividends." From Boats to Brokers From the Dutch East India Company to Wall Street, the stock market has a long and storied history.