DEFINITION of 'TimeVarying Volatility'
Fluctuations in volatility over time. Volatility is the standard deviation of returns from a financial instrument, and hence a measure of its risk. Timevarying volatility implies that volatility is itself subject to large swings, with stocks and other financial instruments exhibiting periods of high volatility and low volatility at various points in time.
INVESTOPEDIA EXPLAINS 'TimeVarying Volatility'
For example, volatility of the S&P 500 Index was unusually low during the 200307 bull market, but reached record levels during the creditcrunchinduced market crash of 2008.
Economist Robert F. Engle, along with Clive Granger, won the 2003 Nobel Memorial Prize in Economics for his groundbreaking analysis of economic time series with timevarying volatility.

Robert F. Engle III
An American economist who won the 2003 Nobel Memorial Prize in ... 
Volatility
1. A statistical measure of the dispersion of returns for a given ... 
Implied Volatility  IV
The estimated volatility of a security's price. In general, implied ... 
Time Series
A sequence of numerical data points in successive order, usually ... 
VIX  CBOE Volatility Index
The ticker symbol for the Chicago Board Options Exchange (CBOE) ... 
Strike Width
The difference between the strike price of an option and the ...

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Options & Futures
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Investing
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Options & Futures
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Options & Futures
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Options & Futures
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Investing Basics
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Gamma is a measurement of how fast the delta of an option’s price changes after a 1point movement in the underlying security. 
Economics
Explaining the Liquidity Coverage Ratio
The liquidity coverage ratio requires banks and other financial institutions to hold enough cash and liquid assets on hand to weather market stress. 
Fundamental Analysis
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Valuation is the process of determining what an asset is worth. 
Economics
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