Gen Xers fret over Social Security. "I will likely be working in retirement."

Retirement is biting Generation X. Its oldest members will turn 62 next year, the earliest age at which people can claim Social Security benefits, with many Americans having too little saved to stop working even as the program faces its own funding crisis.

Chris Branaman, 53, jokes that his retirement will be spent as a Walmart greeter.

"That's my funny way of saying I will likely be working in retirement," said Branaman of Bay City, Michigan, who works in IT and says he has about $100,000 saved in his 401(k) plan. He doesn't expect that will be enough to fund his retirement, even if he's able to put more money away over the next decade.

Branaman is hardly alone. Gen Xers, who are now 46 to 61 years old, entered the workforce in the 1980s and 1990s, just as employers were shifting away from pensions in favor of 401(k)s.

In the 1970s, about half of all private-sector workers had pensions, which are employer-funded and guarantee a payout at retirement. Today, only about 14% of private-sector workers have pensions, a major transformation in the retirement landscape that experts cite as one reason many Americans are woefully short on savings .

The fundamental shift toward 401(k)s places the onus on employees to decide how much to save and to plot out their investment strategy. As a result, many Gen Xers are now realizing that Social Security may end up serving as their primary — or even only — source of retirement income. The 401(k) system hasn't worked for them, several workers in the cohort told CBS News.

Compounding their concerns is a projected Social Security funding shortfall in 2032, which could trigger benefit cuts just as many Gen Xers are set to retire.

Gen Xers cited headwinds ranging from structural issues — automatic enrollment wasn't available when they started working, while some didn't always have access to retirement plans at times in their careers — to economic and personal crises, with job losses and divorce causing some to dip into their retirement savings to get by.

"Maybe we didn't think about it as much early on, just because we were so used to seeing previous generations taken care of by their employers," Branaman said. The 401(k), he added wryly, "was perfect for our generation: Figure it out."

About 41% of U.S. workers over 55 expect Social Security to be their primary source of income in retirement, up from 25% last year, according to a recent survey from financial services firm NFP. That far outpaces the 26% in the same age group who believe their retirements will be mostly funded by 401(k)s, IRAs and other retirement accounts, the poll found.

This data "is a warning light," Jessica Espinoza, NFP managing director and national practice leader for retirement, told CBS News.