The question of which data source to trust for retirement plan cost benchmarking has significant implications for plan sponsors’ fiduciary decisions. This research paper compares two commonly used data sources—the US Department of Labor’s Form 5500 regulatory filings and CEM Benchmarking’s specialized database—by analyzing 59 defined contribution plans that appear in both datasets. The study examines four key cost categories and investigates how different data collection methodologies inform benchmarking conclusions. It explores the structural factors that drive discrepancies between regulatory and specialized data sources, including reporting complexities, accounting variations, and data validation processes. The analysis reveals fundamental differences in how these sources capture and categorize plan costs, with important implications for plan governance decisions. 

Whether you’re a plan sponsor, consultant, or pension professional responsible for cost oversight, this research offers critical insights into the reliability of different benchmarking approaches—and why your data source choice matters for effective fiduciary decision-making.