I worked up a quick present value analysis in excel to get at the original question posed. The analysis included scenarios of living to 70, 80, 90. Obviously lifespan matter in the analysis. If you plan to live a long while, then starting your SS draw later has higher NPV.
My planning strategy at this point will be to assume the least advantageous draw (begin at 62) as a worst case scenario in my projections and then delay if the income is not needed.
Next, I need to incorporate dual strategies that include my younger wife and spouse benefits into the mix.
There is a series of papers by Slavov and Shoven that address this topic in extensive detail.
The determination of when to take benefits with the 62-70 age range depends on two main variables: (1) whether you think your life expectancy is greater or less than the mean life expectancy for your condition (age, gender etc); and (2) the real interest rate at the time you make the decision to delay for another year (or shorter period).
Two resources are needed to determine whether to delay taking benefits: (a) the changes in monthly payouts with age; and (b) the social security actuarial life table, both of which I've linked to below:
http://www.ssa.gov/OACT/ProgData/ar_drc.htmlhttp://www.ssa.gov/OACT/STATS/table4c6.htmlI'll provide one example using male life expectancy from the actuarial table for a person born in 1960. In theory, hundreds of calculations could be made since the SS benefit amount increases in one-month or two-month periods - one is not limited to waiting a whole year to get a benefit increase.
I will use generic units. These can be readily scaled to actual dollars.
At age 69, the monthly benefit is 124, and at age 70 is 132.
The life expectancies for this person are14.4 at age 69 and 13.73 at age 70.
This provides total expected benefit amounts according to the following:
Age 69: 124*14.4 = 1785.6
Age 70: 132*13.73 = 1812.36
Thus the mean expected lifetime SS benefit at age 70 is about 1.5% greater than at age 69 (NOT the commonly touted "8%" figure commonly cited on network news programs).
Does that mean one should necessarily wait until age 70? It depends.
The prevalence of low real interest rates (which is our current situation), shifts the decision towards delaying taking benefits.
Moreover, a belief that your life expectancy is greater than the mean also shifts the decision toward waiting.
Another factor is the balance of concerns between taking benefits early or late.
Even assuming one's life expectancy exactly matched the mean, and that current real interest rates were 1.5%, thereby making the benefits at age 69 and 70 actuarially equal, there is still an argument in favor of waiting.
Specifically, if you take benefits at 70 and unexpectedly become ill at 75, at worst you could lie in bed and ponder what additional fun you might have had between 62 and 70 had you taken benefits earlier.
On the other side of things, if you live to be 85 and beyond, and have to live on a reduced income, you will regret having taken benefits early, over an extended period.
Thus, I expect to wait until age 70 to take benefits and would need a very good reason to do otherwise.