Waiting-time distribution for a stock-market index

Abstract

We investigate the waiting-time distribution of the absolute return in the Korean stock-market index KOSPI. We define the waiting time as a time interval during which the normalized absolute return remains continuously below a threshold $r_c$. Through an exponential bin plot, we observe that the waiting-time distribution shows power-law behavior, $p_f(t)\sim t^{-\beta }$, for a range of threshold values. The waiting-time distribution has two scaling regimes, separated by the crossover time $t_c\approx 200$ min. The power-law exponents of the waiting-time distribution decrease when the return time $\Delta t$ increases. In the late-time regime, $t>t_c$, the power-law exponents are independent of the threshold to within the error bars for fixed return time.