Measures of globalization based on cross-correlations of world financial indices

The cross-correlation matrix of daily returns of stock market indices in a diverse set of 37 countries worldwide was analyzed. Comparison of the spectrum of this matrix with predictions of random matrix theory provides an empirical evidence of strong interactions between individual economies, as manifested by three largest eigenvalues and the corresponding set of stable, non-random eigenvectors. The observed correlation structure is robust with respect to changes in the time horizon of returns ranging from 1 to 10 trading days, and to replacing individual returns with just their signs. This last observation confirms that it is mostly correlations in signs and not absolute values of fluctuations, which are responsible for the observed effect. Correlations between different trading days seem to persist for up to 3 days before decaying to the level of the background noise.