Capital Allocators – Inside the Institutional Investment Industry Daniel Mahr – Glass Box Quant at MDT Advisers (EP.472)
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Nov 20, 2025 
Daniel Mahr, head of the quantitative equity investing group at Federated Hermes, shares insights from his extensive career. He discusses his journey from flipping IPOs to developing sophisticated decision tree models for stock selection. Mahr explains the balance between analytical rigor and human judgment, emphasizing a 'glass box' approach to transparency. He also explores challenges like overfitting and the impact of market changes on strategies, highlighting how quirky factors influence outcomes. Mahr's passion for evolving models fuels continuous improvement in the unpredictable world of investing.
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Prune Factors With Long-Term Tests
- Remove factors only after testing their impact on long-run portfolio outcomes.
- If removing a factor shows little change across decades, you can safely drop it.
From One Tree To Forests
- MDT evolved from one decision tree to forests of shallow trees as compute rose.
- They summarize thousands of trees with tools rather than printing them out on the wall.
Start Broad, Then Find Exceptions
- Trees often start with universal questions like financing activity and then branch.
- Even risky groups (high financing) can contain outperformers identified by momentum or other traits.
