Chapter II: This survey looks at historical volatility of Aetna Inc. prices. The risks associated with long and short term positions can be evaluated according to projected shapes of the Volatility Curve. |
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This chart shows Volatility for Aetna Inc., defined to be the price range as a portion of the average price: So, to derive the Daily Volatility on 2/18/2011 of 1.3%, the price range for the day (0.53) was divided by the average price (38.38). The Daily Volatility is obtained by dividing the daily range by the daily average. A longer Volatility period such as Weekly Volatility is obtained by dividing the weekly price range by the weekly mean price. This is a different concept from the weekly average of daily volatility. The red plot shows the actual price. Volatility, as measured through various intervals, ( Daily, Weekly, Monthly and Quarterly) is plotted according to color. Investors often make a distinction between the concept of Volatility, and the concept of Risk. Academics define them to be exactly equivalent, but as can be seen here, there is good reason to distinguish between the levels of volatility or risk experienced across different time frames. During 31 years, the Average Quarterly Volatility of AET stock price has been 24% while the Average Daily Volatility has been 2%. |
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You may be familiar with the "yield curve" which shows how interest bearing yields vary according to term. Each Volatility Curve is a snapshot in time. As the timespan across which Volatility is measured increases, the Volatility is expected to increase. The relationship between the length of time, and the expected change in price, is not linear, as is demonstrated by this chart. |
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A frequency distribution of the green points on the first chart (the daily volatility) yields this histogram. |
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In a similar vein, the Frequency Distribution of the Quarterly Volatility is plotted here. This is the distribution of the values plotted in purple on the top chart from this page. |
Refined Volatility Risk Analysis for AET : |
| Friday, February 18, 2011: We have news on Fiserv, Inc., ticker symbol FISV. Signs of an over-bought condition have become noticable. Also, there are breaking events concerning Zimmer Holdings, Inc. and McCormick & Company, Incorporated. From the News Archive: (2/18/2011 ) Bad news came from Reynolds American, Inc., Dollar Tree, Inc., Zimmer Holdings, Inc., and NVIDIA Corp. |