Estimating Stock Beta with Regression and Applying It to Market Risk
Summary
The document explains beta as a historical estimate of how an asset’s returns move relative to a market benchmark. A regression of asset returns on benchmark returns estimates beta as the slope, while the intercept represents historical excess return in the model. It relates beta to systematic risk, gives examples of higher and lower beta stocks, distinguishes asset beta from equity beta by noting the latter includes leverage, and describes beta hedging as one potential use. It also introduces the Capital Asset Pricing Model as a way to connect beta with expected return.
An example reports a beta estimate for Google relative to the S&P 500, but the article provides little detail about the sample period or data choices behind it. Beta is backward-looking and may become unreliable after business or capital-structure changes; newer stocks may also lack sufficient price history. The text contains a reversed covariance and variance expression in one formula, although it later states the standard regression slope relationship correctly. Historical beta is therefore a limited risk estimate, not a guarantee of future movement or performance.
Key ideas
- Beta is the regression slope of asset returns against benchmark returns and estimates market sensitivity.
- A beta above or below one indicates greater or lesser historical sensitivity to benchmark moves.
- Equity beta reflects leverage, while asset beta is described as excluding debt effects.
- Beta can inform market-risk hedging, but historical estimates may fail after material company changes.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.