Just to clarify, did you really wait to claim until you were 70 1/2?
Currently, there are no delayed retirement credits beyond age 70, so there is no point in waiting to file beyond this age (other than potentially losing out on back-benefits).
Perhaps you're thinking of the age when you have to start drawing required minimum distributions (RMD) from IRA's, which is 70 1/2?
Not that this affects my original reply.
@bp070202 wrote:
I took delayed retirement at age 70 1/2. My wife, 10 years younger, will recieve 50% of my FRB calculated at my FRA if she retires at 66 1/2, assuming her own benefit is less than 50% of mine. My question is, since my monthly benefit at 70 1/2 is more than it would have been at my FRA, what is my FRA amount for calculating her benefit: what I get now after delayed retirement or what it would have been if I had not delayed (much less)?