There are basically two broadly different quantitative analyses you can perform to assess managers: historical returns based analysis and holdings based analysis. Historical returns based analysis uses manager returns data exclusively. As such, ascribing what drove performance can only be achieved by comparing or regressing those returns against some benchmark or factor index. By contrast, because holdings based data actually provides data on the underlying holdings of the manager, as well as their buying and selling decisions, an analyst can delve into exactly what the fund manager was actually holding that could potentially explain performance.