It seems that Social Security is not the only retirement program that is paying out more than it takes in.

According to a recent Wall Street Journal report, 2013 marked the first year that the amount of money withdrawn from 401(k) plans exceeded the amount contributed. As with Social Security, the shift reflects demographics changes as more Baby Boomers retire from the workforce and begin tapping their savings, while younger workers put smaller amounts in.

Company-sponsored 401(k) plans had $4.6 trillion in assets last year, according to the Investment Company Institute. The average 401(k) balance at the end of the first quarter was $91,800, up 0.5 percent from the fourth quarter of 2014 and up 3.6 year-over-year, according to Fidelity. For employees in a plan for 10 years or more, the average balance was $251,600, up 12 percent year-over-year. 

Workers can contribute up to $18,000 in pre-tax dollars to their 401(k) plans in 2015, but most workers—especially younger ones—save far less each year. There are lots of reasons millennials may be lagging in retirement savings: large numbers of them are still unemployed or underemployed in jobs that don’t have retirement benefits, and they’re diverting all their extra cash to student loans. Plus, retirement may not be top-of-mind for 20-somethings, no matter how many times they hear about the benefits of compound interest.