I had never heard of this notch issue so I googled and found the following on SSA.gov
"Notch" year beneficiaries' principal argument is that they have been singled out to receive lower benefits. But the Commission found no evidence to support that position; indeed, the purpose of the 1977 legislation was to reduce benefits for all future beneficiaries, and it has generally done that.
In fact, considering the value of their benefits relative to the Social Security taxes which they paid, those born in the "Notch" years are, in general, receiving a greater return from Social Security than will subsequent generations of beneficiaries. In addition, their "replacement rate"Cthe percentage of pre-retirement earnings replaced by benefit paymentsCis equal to that of retirees who follow them, which was also the intent of the 1977 amendments. In this sense they are "doing well" as beneficiaries of the system, although not as "well" as those who came before them,(8) especially those who worked well beyond 62.
To the extent that disparities in benefit levels do exist, they exist not because those born in the "Notch" years received less than their due; they exist because those born before the "Notch" years (who were "grandfathered" under the old law's more generous computational method) continue to receive substantially inflated benefits. This disparity has created an understandable perception of unfairness.