Automatic enrollment was supposed to be the magic pill to help employers painlessly increase participation rates in their 401(k) plans. And while that may prove to be the case over the long term, one thing is becoming quite clear right now: Automatic enrollment doesn’t mean automatic results.

Despite the best efforts of many plan sponsors, participation rates in a survey of more than 400 corporate plan sponsors remained basically the same over the past two years—on average, 76 percent of employees now participate in their company’s 401(k) plan, according to a new study by Deloitte Consulting.

That’s just a slight uptick from Deloitte’s 2006 survey, which found that three-quarters of workers were enrolled in their employers’ 401(k) plans.

The marginal increase in participation rates, oddly, occurred during a time in which the number of companies automatically enrolling workers in 401(k) plans nearly doubled. About 42 percent of the plan sponsors polled by Deloitte have an automatic-enrollment feature now, compared with 23 percent two years ago.

There may be a simple explanation, however, for these seemingly contradictory results. The vast majority—roughly 66 percent—of companies that automatically enroll their workers in 401(k) plans are doing so only for new hires.

Less than a third of companies enroll their entire workforce when they add the auto-enroll feature.

Source: Mark Bruno of Financial Week.