We focus on finite sample properties of two mostly used methods of Hurst exponent H estimation – R/S analysis and DFA. Even though both methods have been widely applied on different types of financial assets, only several papers have dealt with finite sample properties which are crucial as the properties differ significantly from the asymptotic ones. Recently, R/S analysis has been shown to overestimate H when compared with DFA. However, we show on the random time series with lengths from 2^9 to 2^17 that even though the estimates of R/S are truly significantly higher than an asymptotic limit of 0.5, they remain very close to the estimates proposed by Anis & Lloyd and the estimated standard deviations are lower than the ones of DFA. On the other hand, DFA estimates are very close to 0.5. The results propose that R/S still remains useful and robust method even when compared to newer method of DFA which is usually preferred in recent literature.

R/S analysis and DFA: finite sample properties and confidence intervals

Exchange market efficiency in iran

According to Efficient Market Hypothesis (EMH) prices completely reflect all available information. Under this condition, it is not possible to speculators to predict the future behavior of asset prices and to earn excess profits in a systematic manner. This study examines efficient market hypothesis in Iranian foreign exchange market during time period 21:03:2002-17:06:2010 by using Detrended Fluctuation Analysis (DFA) technique as well as unit root tests including Augmented Dickey Fuller (ADF) and Philips-Peron (PP). Results indicate that the market was weakly efficient during the selected time period. However, it seems that this efficiency is not due to informed behavior of traders but foreign exchange interventions under managed floating regime. In case that the government adopts floating exchange rate regime in the future, prominent acting of the informed speculators and making depth of the foreign exchange market may prevent dramatic foreign exchange market inefficiency and its consequences.

Shahrazi Mahdi

Papers

An examination of foreign exchange market efficiency hypothesis: a case study of iran