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Using Fama–French Alpha to Study Single-Stock Returns

Article Quant Q&A · Author: Daria Diachenko
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Summary

The document considers whether Fama–French risk-adjusted alpha can be estimated for individual stocks in a study of corporate culture and returns. The proposed analysis estimates monthly risk-adjusted returns from rolling regressions, compounds them into quarterly returns, and relates those returns to lagged culture measures. The response explains that factor models are commonly used to test whether a strategy or anomaly earns returns beyond passive exposure to established risk factors; CAPM performs a related role with only market exposure.

It does not identify a fundamental obstacle to estimating Fama–French alpha for a single stock, but it cautions that the model may not suit the research question. Culture measures could correlate with characteristics represented by factors such as size or value, so controlling for those factors may remove variation the study intends to examine. The answer suggests examining comparable subsamples as one possible alternative. It offers methodological considerations rather than a formal assessment of the proposed panel design, and gives no empirical results or definitive recommendation.

Key ideas

  • Factor-model alpha measures returns beyond exposure to the model’s specified risk factors.
  • Fama–French alpha can be considered for individual stocks, although its suitability depends on the research question.
  • Corporate culture measures may correlate with size or value characteristics represented by model factors.
  • Subsample analyses based on characteristics used to construct factors may help examine those relationships.

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# Fame-French alpha for a single stock


# Fame-French alpha for a single stock












I want to study the impact of corporate culture on risk-adjusted stock returns. After quantifying corporate culture I wanted to use panel methodology (I have a sample of 100 S&P500 companies over 10 years) to study the question. As for the risk-adjusted returns I use Jensen's alpha from CAPM and Treynor measure and estimate those using rolling regressions of the previous 36-months returns for each month. After estimating monthly alphas for each stock, I calculate cumulative quarterly alphas ((1+r_m1)(1+r_m2)(1+r_m3)-1) and regress quarterly alphas on one-period lagged corporate culture measures. However, I also want to calculate alphas using Fama-French model. Can I do it for single stocks and proceed in the same fashion? I read journal articles and I found no paper where an author would calculate alpha for a single stock... everywhere portfolios are constructed. Can anyone explain to me the reason why constructing portfolios are favourable and assess my model? Does it make sense to calculate alphas for single stocks?

Thank you!

## Answer by Ana (score 1)

https://quant.stackexchange.com/a/27874

The reason for using Fama French for portfolios is generally that you try to quantify whether your anomaly/strategy etc. is actually capable of providing returns in excess of what could be achieved by passive exposure to the known risk factors included in the model. CAPM essentially does the same but only looks at the passive exposure to market index.

I don't know if there is necessarily any methodological problems with using Fama French model to estimate the alpha for a single stock, but I think it makes a lot of sense to consider if it is the right tool in your case.

I would carefully consider what you want to measure - I would imagine, that certain measures of corporate culture would be significantly correlated with some of the Fama French factors. Without knowledge of the list of variables you plan on investigating, I would still assume that smaller companies probably have very different cultural characteristics than larger companies, and same most likely applies to value factor (think e.g. Facebook vs. Morgan Stanley). Hence it might not make a lot of sense to capture this variation using FF model - you could, however, run the same analysis with subsamples using similar criteria as is used in construction Fama French factors if that interests you.

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