Stock Beta Computation, 6 Closing Thoughts

When I wrote about computing stock betas in 2010, I had no idea it would be this blog’s third most popular topic. I wrote a handful of blog posts about stock beta, but my heart wasn’t in them.  Today, driving home from the airport, I was inspired to blog about beta for perhaps the last time.  Previously I held back and focused on the mechanics of beta computation, and the discrepancies I was seeing between various website’s beta values.  This time I provide an example beta-computation spreadsheet and don’t hold back on the math or the theory.  Before I launch into this final word on beta, here a few highlights.

  1. Beta is easy to find online.  Not all sites agreed on value, but the delta seems less than it was 2 years ago.   Why compute beta when you can simple look it up?
  2. Beta is less useful if it has a low R-squared.  Luckily, sites like Yahoo! Finance provide R-squared values.
  3. Even with a high R-squared, beta is not a very useful risk measure.  Standard deviation is better in many ways.
  4. In theory high-beta stocks (>3) should go up dramatically when the market goes up.  In practice this is often not the case.
  5. In theory low-beta stocks (<0.5) should be “safer” than the market.  Again not so true.
  6. In theory low-beta stocks (<0.5) should “under-perform.”  Not necessarily.

If you are still interested in beta, simply click to read the full-beta blog.

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