Automatic enrollment in a defined contribution plan has been allover the news as a means of increasing participation among workersand getting them better prepared for retirement—but that doesn’tmean it’s a cure-all.

In fact, auto-enrolled older workers aren’t as enthusiasticabout contributing to their retirement fund as those who enrollthemselves.

That’s according to a working paper from the Center forRetirement Research at Boston College, which found that olderworkers who are automatically enrolled in their retirementplan at work don’t tend to contribute as much to theplan as workers who have to actively put themselves into theplan.

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The paper also found, however, that, while those workers mightnot be contributing as much, “automatic enrollment is associatedwith an increased probability that older workers’ employers willcontribute to their plans. As a result, employer contributionamounts and contribution rates are higher among auto enrolledworkers than voluntarily enrolled workers.”

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But even though these employers are contributing more on averagethan the employers of other workers who haven’t been auto enrolled,it’s still not enough to make up for the lesser amount thatauto-enrolled employees contribute.

Those employer contributions might be higher than average, butthey aren’t high enough to offset the difference.

As a result, the paper said, “the combined effect is that theretirement accounts of automatically enrolled older workersreceive, on average, $900 less in annual total contributions andhave 1.6 percentage points lower total contribution rates thanthose of voluntarily enrolled workers.”

It’s true that auto enrollment significantly increases workerparticipation. One study cited by the paper found an increase of 48percent among newly hired employees and an 11 percent increase inoverall participation at one company 15 months after it adoptedauto enrollment.

However, since auto-enrolled employees tend to stick withwhatever the default contribution is, and companies routinely setthat bar low—with most setting the default contribution rate belowwhat is required to take full advantage of employer matchingcontributions—those auto-enrolled employees don’t derive the fullbenefits of the plan just because they’re in it.

Employees who must enroll themselves, on the other hand,tend to make higher contributions.