Based on the info sheet I received from the SSA in June of this year
"If you have enough work credits, we estimate your benefit amounts using your average earnings over your working lifetime."
Credits:
You earn one credit for each $1050 of wages or self-employment income. When you've earned $4200 you've earned your four credits for the year. Most people need 40 credits, earned over their working lifetime, to receive retirement benefits.
I just turned 55. Based on what I've earned so far and what they project I will earn until I retire, if I decide to begin drawing my benefits at 62 I would get $1498 per month. If I wait until age 66 (my current full-benefit age), the benefit would be $2056 per month. That jumps up to $2797 at age 70.
Not allowing for any cost-of-living adjustments (same percentage either way but a little more $ calculated on the higher benefit) it would take me until about age 73 to make up the difference of waiting until 66 to begin taking SS benefits.
Right now I'm leaning towards starting at age 62 and taking my chances. Fortunately I won't have to depend solely on my SS benefits.
They included this caveat:
Your estimated benefits are based on current law. Congress has made changes to the law in the past and can do so at any time. The law governing benefit amounts may change because, by 2041, the payroll taxes collected will be enough to pay only about 78 percent of scheduled benefits.
You can find out more on your personal situation at:
http://www.socialsecurity.gov/mystatement/