An Eight-Factor Model for Decomposing Bond Fund Returns

Summary

This report outlines a method for analyzing open-ended bond fund returns and deriving a residual alpha measure for fund screening. It groups risk exposures into eight factors spanning interest-rate curve movements, credit risk, equity markets, and money markets. The rate factors capture parallel shifts and changes in curve slope and curvature; credit factors represent rating-related premia and compensation for default risk. The report also accounts for convertible bond and equity exposures.

To reduce overlap among the factors, the authors reconstruct stock, bond, and money-market index returns using immunization strategies. They then regress fund returns on the resulting factors through time and use the residual as an alpha estimate. In a historical sample of 694 funds, a 20-trading-day lookback reportedly gave the best model fit, and residuals were distributed around zero in a way the authors considered broadly consistent with normality. The document does not show the later fund-selection or portfolio results, and it cautions that historical relationships may change with the economic environment.

Key ideas

• The model decomposes bond fund returns into eight exposures across rates, credit, equities, and money markets.
• Rate exposures distinguish curve level shifts from slope and curvature changes.
• Index reconstruction with immunization is used to reduce correlation among the factors.
• Rolling time-series regression residuals serve as a candidate fund alpha measure.
• The reported fit and residual behavior are historical findings and may not persist.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.