Abstract: |
In this paper, we show how the sampling properties of the Hurst exponent
methods of estimation change with the presence of heavy tails. We run
extensive Monte Carlo simulations to find out how rescaled range analysis
(R/S), multifractal detrended fluctuation analysis (MF-DFA), detrending moving
average (DMA) and generalized Hurst exponent approach (GHE) estimate Hurst
exponent on independent series with different heavy tails. For this purpose,
we generate independent random series from stable distribution with stability
exponent {\alpha} changing from 1.1 (heaviest tails) to 2 (Gaussian normal
distribution) and we estimate the Hurst exponent using the different methods.
R/S and GHE prove to be robust to heavy tails in the underlying process. GHE
provides the lowest variance and bias in comparison to the other methods
regardless the presence of heavy tails in data and sample size. Utilizing this
result, we apply a novel approach of the intraday time-dependent Hurst
exponent and we estimate the Hurst exponent on high frequency data for each
trading day separately. We obtain Hurst exponents for S&P500 index for the
period beginning with year 1983 and ending by November 2009 and we discuss the
surprising result which uncovers how the market's behavior changed over this
long period. |