Clusters or networks of economies? A macroeconomy study through GDP   fluctuation correlations
  We follow up on the study of correlations between GDP's of rich countries. We analyze web-downloaded data on GDP that we use as individual wealth signatures of the country economical state. We calculate the yearly fluctuations of the GDP. We look for forward and backward correlations between such fluctuations. The system is represented by an evolving network, nodes being the GDP fluctuations (or countries) at different times.   In order to extract structures from the network, we focus on filtering the time delayed correlations by removing the least correlated links. This percolation idea-based method reveals the emergence of connections, that are visualized by a branching representation. Note that the network is made of weighted and directed links when taking into account a delay time. Such a measure of collective habits does not fit the usual expectations defined by politicians or economists. 
M. Ausloos and R. Lambiotte