In this study, we have investigated empirically the effects of market properties on the degree of diversification of investment weights among stocks in a portfolio. The weights of stocks within a portfolio were determined on the basis of Markowitz's portfolio theory. We identified that there was...

Symbolic analysis of economic indicators and derived time series offers an advantage of transferring quantitative values into qualitative notions by indexing intervals of numerical data with symbols. While differences in the numerical indicators are routinely measured by subtraction, differences...

Recent works by econo-physicists [5,8,15,19] have shown that the probability function of the share returns and the volatility satisfies a power law with an exponent close to 4. On the other hand, we investigated quantitatively the return and the volatility of the daily data of the Nikkei 225...

In recent years a large number of models of financial markets based on interacting heterogeneous agents have been developed. These models generally allow the size of the different groups of agents to vary according to the evolution of the financial market. Adaptive belief system proposed by...

In this study, we investigate the statistical properties of the stock return volatility, defined as the absolute value of the logarithmic relative price changes. We show examples of power-law and of exponential-law for the volatility observed in the Japanese stock markets, and propose a...

Using the price change and the log return of 10 stock market indices, we examine the temporal evolution of the time scale. The 10 stock markets had similar properties. Their log-return time series had patterns and long-range correlations until the mid-1990s. In the 2000s, however, the long-range...

In this paper, we present an interacting-agent model of speculative activity explaining bubbles and crashes in stock markets. We describe stock markets through an infinite-range Ising model to formulate the tendency of traders getting influenced by the investment attitude of other traders....

The aim of this paper is to investigate the statistical properties of the spatial distribution for each of the towns in Japan, of the number of large income earners living in them and their total income. Using a Japanese database of high-income taxpayers for two consecutive years, 1997 and 1998,...

Pareto's law states that the distribution of personal income obeys a power-law in the high income range. Its dynamical nature has been little studied hitherto, mostly due to the lack of empirical work. Using an exhaustive list of taxpayers in Japan for two consecutive years, when the economy was...