The number of US workers in the labor market over the age of 75 is expected to nearly double over the next decade, creating a looming retirement crisis.

Retirement savings in the United States were long thought of as a three-legged stool. Americans had pension plans, Social Security benefits, and defined contribution plans like the 401(k). Not anymore.

Pension plans are nearly extinct. About half of private sector workers were covered by those so-called defined-benefit plans in the mid-1980s, but by 2022 only 15% of private sector workers had them.

Social Security payments still provide about 90% of income for more than a quarter of older adults, according to Social Security Agency surveys. But the Social Security trust fund is facing a 75-year deficit, and without intervention it will be depleted by the mid-2030s, meaning that only a portion of retirees’ expected benefits will be paid out. Lawmakers have faced a decades-long political stalemate on how to fix it.

What’s left is the 401(k), which 68% of private industry workers have access to, but only 50% use.