A useful way to look at the generousity of Social Security payments is to look at the “replacement rate” of benefits. This can be calculated in various ways, but a standard approach is to compare Social Security payments that would be received by someone at the “normal retirement age” as an average of that person’s top 35 years of pre-retirement earnings–with those earnings adjusted for the growth rate of national average wages over time (and in this way capturing an aspect of both inflation and growth over time). In the early 1970s, the replacement rate went haywire, which is part of what caused the Social Security system to need rescuing in the early 1980s, and what will cause it to need rescuing again by the early 2030s. Andrew Biggs tells the story in “It’s Fine to Embrace FDR’s Vision of Social Security, But You Don’t Need to Embrace Nixon’s and Carter’s” (Little Known Facts, January 29, 2026).
This graph tells the basic story of what happened. Focus first on the line showing replacement rates for a “medium” wage-earner. At the start of the system, the medium wage-earning had a replacement rate of about 24%, but Congress raises this level in the 1950s, and by the late 1960s it’s about 29%. Then there is a dramatic spike: the Social Security replacement rate for a medium earner rises from 29% around 1970 to 51% by 1980. It then sags back down to about 40% by the mid-1980s, where it has stayed since.

Since the beginning of Social Security, the system has been set up so that while those with high incomes did and do receive higher monthly payments, the share of income replaced is higher for those with low incomes. The graph above shows the higher replacement rates for those with lower levels of income. It also shows how the spike in Social Security replacements rates applied to all groups.
So what happened? Biggs lays out details of the timeline, and who knew what. His basic story is that Congress wanted to adjust Social Security for rising inflation, but the formula that was enacted into law (obviously) did a lot more than just keep benefits aligned with inflation. He argues that many members of Congress literally didn’t know what they were doing.
He digs into the background staff reports at the time. For example, who can forget that timeless 1973 blockbuster from the actuaries, “Some Aspects of the Dynamic Projection of Benefits Under the 1972 Social Security Amendments”? Biggs makes the case that, behind the scenes, many staffers knew that the new formula would spike the Social Security replacement rate, but because the staffers wanted that to happen, they didn’t spell it out to Congress. The chief actuary for Social Security said in 1970: “Certain of the top policy-making officials at the Social Security Administration (who are holdovers from the Johnson Administration) have strong beliefs in the desirability—even the necessity—of the public sector taking over virtually all economic security provisions for the entire population and thus eliminating private efforts in this area.”
But the dramatic rise in replacement rates had consequences. According to calculations by Biggs: “Had Social Security replacement rates simply been kept at their 1969 levels, and therefore missed the large benefit increases of the 1970s, the average benefit for a new retiree in 2026 would have been about $20,375, about 25 percent less. That difference alone would have almost certainly avoided Social Security’s near-death experience in 1977, its brush with insolvency in 1983 and the projected exhaustion of the trust funds in 2032.”
Biggs also grasps the nettle of a more difficult policy question: Does this history have lessons for the necessary reform of Social Security finances by the early 2030s? After all, the Social Security reforms of the early 1980s put the system on a path it has followed for the last half-century, andt the reforms of the early 2030s may establish a path all the way to 2100. There are shorter-term and longer-term issues here.
In the shorter-term, there are elderly folks already relying on Social Security, and others who have been planning their retirement based on often-repeated promises of the Social Security income they will receive after retirement. It would seem grossly unfair, even cruel, to break those promises.
But now consider those born since, say, 2020. That generation will not enter the workforce in a significant way until 2040, and some of them (say, those who attend college and graduate school) until later than that. At this point, and by early 2030, they will not have paid any taxes into the Social Security system, and they have not built their financial futures based on, say, what their retirement income will look like when they turn age 65 in 2085. It would not be unfair or cruel to redesign Social Security for that generation.
Biggs puts forward his own view of what should happen. He points out that that when Social Security was first enacted in the 1930s, it was in an economy where very few people had private pension, and self-owned contributory retirement accounts like IRAs and 401k accounts didn’t exist. As he writes, it is “far, far easier for middle- and high-income Americans to save for retirement on their own today than it was in the world of 1935.” Thus, Biggs suggests that for this next generation, Social Security reforms should transition to a flat benefit, received by every elderly person, that would provide a robust above-the-poverty-line safety net for all seniors.
I’m uncertain about that recommendation. Part of the allure of Social Security is that it has not been a pure safety-net program for the elderly poor. Instead, even though it has always involved some redistribution from high- to low-incomes, the benefits you receive are linked, to some extent, to what you paid into the system.
However, Biggs seems clearly correct on three points. First, the financial ecosystem that helps those with middle- and high-incomes save for retirement is quite a bit different than in the 1930s. Second, the current replacement rates and tax rates in Social Security are not the original vision of the program. Instead, the current replacement rates were foisted on the public without discussion in the early 1970s, and the current tax rates were enacted in the early 1980s to as necesary to support those higher replacement rates. Third, when Congress gets around to redesigning the future of Social Security–probably in the early 2030s–for the future generations who are born only recently, or not yet born at all, we should not treat the current structure of Social Security as sacrosanct.















