401(k) accounts are far from perfect as a retirement benefit, but they are getting better, and more improvements are on the way.

For better or worse, private-sector employers have largely substituted the 401(k) for the good old-fashioned defined-benefit pension in recent decades. Not all workers had traditional pensions even in their peak years, but those who did benefited from automatic participation, professional investment management and a guaranteed lifetime income stream when they retired. With a 401(k), you’ve got an employer-managed, tax-deferred retirement account that allows you to invest part of your salary in a variety of mutual funds. The risk and responsibility is all yours, and translating whatever you have saved into income is challenging.

The most significant improvements to these plans over the past couple of decades have added more automatic processes and decisionmaking. Since Congress passed the Pension Protection Act of 2006, a majority of plan sponsors have made enrollment automatic for workers when they start new jobs. Another improvement is the dominance of target-date funds, which automatically adjust the allocation of equities and fixed income as retirement draws near.

The changes have improved investor behavior. Among workers who have access to a plan, participation and savings rates are rising. That’s the good news. The flip side of this coin is a huge coverage problem. Only about half of private-sector U.S. workers are covered by a workplace plan at any given time, and most of them work for larger firms that tend to have well-run, low-cost plans that keep more money in the pockets of savers.

In my Reuters column this week, I consider the improvements that have benefited 401(k) savers, and the changes we still need if the system is benefit a wider group of retirees.