Travel and tourism: Into a complex network
  It is discussed how the worldwide tourist arrivals, about 10% of world's domestic product, form a largely heterogeneous and directed complex network. Remarkably the random network of connectivity is converted into a scale-free network of intensities. The importance of weights on network connections is brought into discussion. It is also shown how strategic positioning particularly benefit from market diversity and that interactions among countries prevail on a technological and economic pattern, questioning the backbones of traveling driving forces. 
J.I.L. Miguens, J.F.F. Mendes