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If you want evidence that the 401(k) plan has been a failed experiment, consider how they're starting to resemble the traditional pensions they've largely replaced. Plan by plan, employers are moving away from the do-it-yourself free-for-all of the early 401(k)s toward a focus on secure retirement income, with investment pros back in charge of making that happen.

We haven’t come full circle—and likely never will. The days of employer-funded, defined-benefit plans with guaranteed lifetime income will continue their three-decade fade to black. But the latest 401(k) plan innovations have all been geared at restoring the best of what traditional pensions offered.

Wall Street wizards are hard at work on the lifetime income question. Nearly all workers believe their 401(k) plan should have a guaranteed income option and three-in-four employers believe it is their responsibility to provide one, according to a BlackRock survey. So annuities are creeping into the investment mix, and plan sponsors are exploring ways to help workers seamlessly convert some 401(k) assets to an income stream upon retiring.

Meanwhile, like old-style pensions, today’s 401(k) plans are often a no-decision benefit with age-appropriate asset allocation and professionally managed investment diversification to get you to the promised land of retirement. Gone are confusing sign-up forms and weighty decisions about where to invest and how much to defer. Enrollment is automatic at a new job, where you may also automatically escalate contributions (unless you prefer to handle things yourself and opt out).

More than anything, the break-neck growth of target-date funds has brought about the change. Some $500 billion is invested in these funds, up from $71 billion a decade ago. Much of that money has poured in through 401(k) accounts, especially among our newest workers—millennials. They want to invest and generally know they don’t know how to go about it. Simplicity on this front appeals to them. Partly because of this appeal, 40% of millennials are saving a higher percentage of their income this year than they did last year—the highest rate of improvement of any generation, according to a T. Rowe Price study.

With a single target-date fund a saver can get an appropriate portfolio for their age, and it will adjust as they near retirement and may keep adjusting through retirement. About 70% of 401(k) plans offer target-date funds and 75% of plan participants invest in them, according to T. Rowe Price. The vast majority of investors in target-date funds have all their retirement assets in just one fund.

“This is a good thing,” says Jerome Clark, who oversees target funds for T. Rowe Price. Keeping it simple is what attracts workers and leads them to defer more pay. “Don’t worry about the other stuff,” Clark says. “We’ve got that. All you need do is focus on your savings rate.”

Even as 401(k) plans add features like auto enrollment and annuities to better replace traditional pensions, target-date funds are morphing too and speeding the makeover of the 401(k). These funds began life as simple balanced funds with a basic mix of stocks, bonds and cash. Since then, they have widened their mix to include alternative assets like gold and commodities.

The next wave of target-date funds will incorporate a small dose of illiquid assets like private equity, hedge funds, and currencies, Clark says. They will further diversify with complicated long-short strategies and merger arbitrage—thus looking even more like the portfolios that stand behind traditional pensions.

This is not to say that target-date funds are perfect. These funds invest robotically, based on your age not market conditions, so your fund might move money at an inopportune moment. Target-date funds may backfire on millennials, who have taken to them in the highest numbers. Because of their age, millennials have the greatest exposure to stocks in their target-date funds and yet this generation is most likely to tap their retirement savings in an emergency. What if that happens when stock prices are down? Among still more concerns, one size does not fit all when it comes to investing. You may still be working at age 65 while others are not. That calls for two different portfolios.

But the overriding issue is that Americans just don’t save enough and a reasonably inexpensive and relatively safe investment product that boosts savings must be seen as a positive. With far less income, millennials are stashing away about the same percentage of their earnings as Gen X and boomers, according to T. Rowe Price. That’s at least partly thanks to new-look 401(k)s and the target-date funds they offer.

Read next: 3 Ways to Build a $1 Million Nest Egg Despite Lower Investment Returns