Before revision:   Our data analysis of six major indices suggests that the actual interaction structure is mathematically equivalent to an Ising model on a complete graph with gaussian interaction strengths scaling as the inverse of the system size.
After revision:  This is done with an approach only based on empirical data of price returns. Our data analysis of six major indices suggests that the actual interaction structure is mathematically equivalent to an Ising model on a complete graph with gaussian interaction strengths scaling as the inverse of the system size.