This article consists in three parts. The first part deals with theory. We evaluate the pros and cons of government … neglected the latter (like Japan, Spain, etc.). In the third part, we use the theory and the international policy parts to …

We survey the literature on social networks by putting together the economics, sociological and physics … not explain why they emerge. On the contrary, the economics approach is very precise in explaining why networks emerge but … results with those obtained in sociology. -- random graph ; game theory ; centrality measures ; network formation ; weak and …