If you're like most Americans, Social Security is going to be a very important source of income when you retire. It's also one of the most flexible sources of retirement income people have access to, with retirees able to start receiving benefits anytime between age 62 (at a reduced monthly benefit) and 70 (at an increased benefit). According to research at Boston College (covered by my colleague Matt Frankel), 62 is by far the most common age for people to claim Social Security.