Thanks for the responses so far!
Sorry, I was not clear.
I went to a retirement planning seminar (not in any way a sales pitch, put on by a retiree from my company and very well done). He mentioned that Social Security was never meant to provide all retirement income but rather X % of retirement income and he noted that that number is pretty close to what the average amount for retirees is now. I'll tell you the actual % he gave in a few days.
He speciifically said "income" but included investment returns and withdrawals and one source of income, pensions being the other.
So I guess given that net income=expenses by definition for a retiree, % of expense would give the same answer. (If your income exceeds your enpenses that excess just goes back into savings, right)
I'm interested in seeing if the experience of people here is close to the average and the original intent of SS. If you are not yet taking SS then I would say it does not make sense to answer unless you want to report what you plan it to be.