Normally, your SS retirement payment is based upon your 35 highest years of your employment salary. But, how does SS handle this when you don't have 35 years of employment because you were on SSDI part of your adult life. If you were on SSDI at the time you became age 66, then you just get SS the same as your SSDI payment. The 35 year computation is not used. But what happens if you were on SSDI and you worked briefly before you turned 66 but you do not have 35 years of employment. How is your SS retirement benefit calculated>