Evaluating Long-Short Factor Replication of a Long-Only Portfolio

Summary

This question considers whether a long-only portfolio can be explained or replicated using a linear combination of long-short factor returns, such as Fama–French factors or Betting Against Beta. The proposed analysis is a return regression: factor coefficients estimate exposures, while the coefficient of determination summarizes the share of observed portfolio-return variance explained by the selected factors. The author reports an R-squared of about 0.6 and three statistically significant factor coefficients, then asks whether that comparison is meaningful.

The document supplies no response, regression details, sample period, benchmark, or out-of-sample evidence. It therefore does not establish that the factors create a realizable long-only replication or that the estimated relationship is stable. A regression can describe return co-movement, but assessing a portfolio replication would also require attention to factor construction, investability, costs, leverage, constraints, and residual risk. These are evaluation considerations, not conclusions provided by the source.

Key ideas

• A return regression can estimate a long-only portfolio’s exposures to long-short factors.
• The coefficient of determination measures explained return variance, not necessarily successful portfolio replication.
• Statistically significant coefficients indicate estimated relationships within the fitted sample.
• The document reports an approximate R-squared and significant coefficients but gives no sample or validation details.
• Investability, costs, constraints, and residual risk are not addressed in the question.

Tags

# Constructing a replicating portfolio of a long-only strategy using long-short factors


# Constructing a replicating portfolio of a long-only strategy using long-short factors












Lets say I want to estimate a replicating portfolio by doing a linear regression between the returns of a long-only portfolio and several long-short factors like Fama-French 5-factor or Betting Against Beta (CAPM framework).

I discover that I can replicate and explain about 60% of the variance in my long-only portfolio ($R^2$ of ~0.6) with 3 significant coefficients to some of the long-short factors mentioned above. Does this comparison even make sense when replicating a long-only strategy with multiple long-short strategies?

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