A log-periodic fit for the flash crash of May 6, 2010

We show that a two-harmonic log-periodic formula fits the high-frequency data from the Dow Jones Industrial Average index, which encompass the recent episode known as the “flash crash†of May 6, 2010.flash crash, crashes, log-periodicity

The relative efficiency of stockmarkets

Financial economists usually assess market efficiency in absolute terms. This is a shortcoming. One way of dealing with the relative efficiency of markets is to resort to the efficiency interpretation provided by algorithmic complexity theory. This paper employs such an approach in order to rank 36 stock exchanges and 37 individual company stocks in terms of their relative efficiency.

Scaling power laws in the Sao Paulo Stock Exchange

The scaling of the probability distribution of the Sao Paulo Stock Exchange index is shown to be described by a Levy stable stochastic process for the modal region of the distribution. Data refer to daily records for the 30-year period 1968-1998. The truncated Levy process is characterized by a scaling index of 1.66. Scaling power laws are also shown to be present in the mean and standard deviation of the series as the time horizon is increased. A power law is also found for the autocorrelation time of the natural logs of the index series. The deviations from the line that best fits the natural logs of the series are also found to be short range autocorrelated and to follow an exponential decay.complex systems

Biological correlates of the Allais paradox

We conducted a questionnaire study with student subjects to look for explicit correlations between selected biological characteristics of the subjects and manifestation of the Allais paradox in the pattern of their choices between sets of two pairs of risky prospects. We find that particular bio-characteristics, such as gender, menstrual cycle, mother’s age, parenthood, digit ratio, perceived negative life events, and emotional state, can be related to the paradox. Women, in particular if not menstruating, are less susceptible to the paradox. Those born to not-too-young mothers are also less prone to the paradox. The same holds true for those who father children, those with high prenatal testosterone exposure, who have reported many negative life events, and those who were anxious, excited, aroused, happy, active, and fresh at the time of the experiment. Further, left-handers and atheists may be less inclined to exhibit the paradox.Allais paradox; choice under risk; biological characteristics

Risk-seeking behavior of preschool children in a gambling task

A recent neurobiology study showed that monkeys systematically prefer risky targets in a visual gambling task. We set a similar experiment with preschool children to assess their attitudes toward risk and found the children, like the monkeys, to be risk seeking. This suggests that adult humans are not born risk averse, but become risk averse. Our experiment also suggests that this behavioral change may be due to learning from negative experiences in their risky choices. We also showed that though emotional states and predetermined prenatal testosterone can influence children’s preferences toward risk, these factors could not override learning experiences.Risk; Children

Biological correlates of the Allais paradox - updated

We conducted a questionnaire study with student subjects to look for explicit correlations between selected biological characteristics of the subjects and manifestation of the Allais paradox in the pattern of their choices between sets of two pairs of risky prospects. We found that particular characteristics, such as gender, menstrual cycle, mother’s age at delivery, parenthood, second- to fourth-digit ratio, perceived negative life events, and emotional state, can be related to the paradox. Women,particularly when not menstruating, are less susceptible to the paradox. Those born to not-too-young mothers are also less prone to the paradox. The same holds true for men who have fathered children and had been exposed to high levels of prenatal testosterone, people who had experienced many negative life events, and those who were anxious, excited, aroused, happy, active, or fresh at the time of the experiment. Further, left-handers and atheists may be less inclined to display the paradox.Allais paradox; choice under risk; biological characteristics; experimental economics

Hurst exponents, power laws, and efficiency in the Brazilian foreign exchange market

We find evidence of weak informational efficiency in the Brazilian daily foreign exchange market using Hurst exponents (Hurst 1951, 1955, Feder 1988), which offer an alternative (from statistical physics) to traditional econometric gauges. We show that a trend toward efficiency has been reverted since the crisis of 1999. We also find power laws (Mantegna and Stanley 2000) in means, volatilities, the Hurst exponents, autocorrelation times, and complexity indices of returns for varying time lags.econophysics

Fractal structure in the Chinese yuan/US dollar rate

Price changes of the Chinese yuan/US dollar rate are found to display a Sierpinski triangle in an Iterative Function System clumpiness test. This fractal structure commonly emerges in “the chaos gameâ€, where randomness coexists with deterministic rules. We show that a threshold model with four states, two deterministic and two stochastic is able to replicate the properties of the yuan/dollar returns in general, and the Sierpinski triangle in particular.