This report compared the performance of the Defined Benefit (DB) and Defined Contribution (DC) plans in the United States.
CEM conducted research on this matter in 2006, and on that occasion concluded that, on average, the DB funds surpassed the DC plans by a total net return difference (total returns minus costs) of 1.8% between 1998 and 2005. If this return difference had been maintained for another 25 years, it would have entailed that a person enrolled in a DC plan would have an average balance of 34% less than a person enrolled in a DB plan.
Nonetheless, updating the data shows that in the last 10 years, between 2007 and 2016, the DB plans have surpassed the DC plans by a mere 0.46% in net return. The report found that the drop in the relative performance of the DB funds with respect to the DC funds can be explained by three factors:

1. A better asset mix in DC plans.
2. Improved design of the DC plans: more automatic enrollment and better default options.
3. Lower cost of the DC plans

To review the importance of the aforementioned factors in greater detail, please review the report here.