During 2006, the most recent year included in the analysis based on pension reports employers file with the federal government, the median rate of return for defined-benefit plans was 12.9 percent, compared with 11.3 percent for 401(k) plans.

The biggest difference in rates of return during the 12-year period was in 2000, when the median rate of return for defined-benefit plans was -0.01 percent, compared with a 2.75 percent loss for 401(k) plans.

Watson Wyatt consultants say it isn’t surprising that rates of returns for defined-benefit plans are outpacing 401(k) plans.

The professionals whom employers retain to manage their defined-benefit plans “have considerable financial education, experience and discipline, as well as access to sophisticated investment tools,” Alan Glickstein, a senior retirement consultant in Watson Wyatt’s Dallas office, said in a statement.

“These advantages, coupled with a much longer investment time horizon, help DB plan sponsors maximize their returns and maintain well-diversified portfolios,” he added.

By contrast, 401(k) plan participants often lack the time to actively manage their investments and also lack professional investment experience, reducing rates of return, Glickstein said.