Finding the influential few. In medicine, in politics, and in social networks….

Nature looks at the star power of “network theory,” curious statistics that control all kinds of complicated systems. They’ve found that even really complex networks are shaped by an influential few:

To demonstrate their technique, Yang-Yu Liu of Northeastern University in Boston and his colleagues looked at the entire human metabolic network and found that concentrations of about 10% of the body’s 2,763 metabolites could be used to determine the levels of all the rest.

But the method could also be used in social networks to identify the people whose opinions determine everyone else’s, helping to predict the outcome of, say, a presidential election. Or it could help ecologists to single out the particular species to track to follow changes in an entire ecosystem, to name just a few potential applications.

Liu’s team tackled the problem by examining clusters of strongly connected components in a network, again represented by nodes with arrows connecting them.

They found that most of the time (and almost always in real-world networks), these selected nodes alone are sufficient to determine the state of every other node in the network.

How drugs affect hormones. How podcasters affect Facebook traffic. How Twitter affects political demonstrations.

Star power.