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. Related Content Imagine your life with guaranteed income If you had guaranteed income, how would you spend your days? An annuity offers the opportunity to find out. How to get your finances ready for retirement To live the retirement you want you need to plan ahead. Taking these steps may help. How can you have guaranteed income in retirement? What is an annuity exactly?