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 Inflation and Your Portfolio Even low inflation rates can pose a threat to investment returns. Mutual Funds vs. ETFs Exchange-traded funds have some things in common with mutual funds, but there are differences, too. 5 Smart Investing Principles Principles that can help create a portfolio designed to pursue investment goals.