On the stock page in yahoo finance, there is specified a beta value for the stock. Now is there a way to know what time period was used to calculate the beta? Is it the trailing 12 months? Does yahoo finance give a way to find beta's for customised time periods?

  • +1 - We hear the term all the time, a discussion of its definition or calculation seems appropriate. – JTP - Apologise to Monica Apr 28 '13 at 16:36

Citing the Yahoo Finance Help page,

Beta: The Beta used is Beta of Equity. Beta is the monthly price change of a particular company relative to the monthly price change of the S&P500. The time period for Beta is 3 years (36 months) when available.

Regarding customised time periods, I do not think so.

  • hey how can it be monthly and also for 3 yrs? – Victor123 Apr 28 '13 at 14:00
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    @franktheshark - +1 I edited your answer for formatting only. There's a quote feature that offer the look as shown now. Also, a direct link, no link services. Welcome to money.SE. – JTP - Apologise to Monica Apr 28 '13 at 14:07
  • @Kaushik - beta addresses how a stock moves compared to the S&P, it's a volatility calculation. When I first looked at the question, it occurred to me that beta might change over time, and needs a timespan for the calculation, but beta itself shouldn't be thought of as "1 month beta" or "1 year beta", it's a pure number. – JTP - Apologise to Monica Apr 29 '13 at 15:35
  • I'm wondering how Google Stock Screener calculates Beta. google.com/finance/stockscreener – Marco Demaio Oct 16 '14 at 17:29
  • @Victor123... think of Beta as the correlation coefficient between the stock market (SP500) and the individual stock you're examining. The '3 year' period is the period over which the correlation is calculated. But the 1 month period is the time over which the data points are taken. I.e. they don't take the change in daily prices of the SP500 vs change in daily price of the stock and calculate correlation, they use the monthly prices. – user23998 Dec 11 '14 at 17:26

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