Annualized Volatility

8 Pages Posted: 19 Feb 2012

Date Written: February 18, 2012


In this research note, we compare S&P 500 volatility figures calculated with the popular “square-root-n rule” to volatility figures derived from time-aggregated daily returns and try to reconcile the differences with popular time-series models featuring serial correlation in returns or volatilities.

We show that the deviations from the square-root-n rule cannot be explained with serial correlation in returns, rather with a GARCH model. We conclude that volatility figures annualized with the square-root-n rule should not be interpreted as accurate estimates for true annual volatility. The square-root-n rule is also not suitable to standardize volatility figures for reporting purposes.

Keywords: Annualized Volatility, Square-Root-N Rule, Autocorrelation, GARCH

Suggested Citation

Steiner, Andreas, Annualized Volatility (February 18, 2012). Available at SSRN: or

Andreas Steiner (Contact Author)

Andreas Steiner Consulting GmbH ( email )

Walderstrasse 43c
Hinwil, 8340

Do you have a job opening that you would like to promote on SSRN?

Paper statistics

Abstract Views
PlumX Metrics