Barabasi notes that others have observed power-law degree distributions. The Italian economist Vilfredo Pareto noticed that 20 percent of his peapods produced 8o percent of the peas-nature doesn't always follow a bell curve. He also found that 8o percent of the land in Italy was owned by 20 percent of the population. In business and management circles, Pareto's law is known as the 8o /20 rule (although he did not use the term) and is said to apply in a variety of instances: "8o percent of the profits are produced by only 20 percent of the employees, 8o percent of customer service problems are created by only 20 percent of consumers, 8o percent of decisions are made during 20 percent of meeting time, and so on" ( 66). Further examples might be Holywood's "A. list" o r the "A list'' that emerged among bloggers. Like scale-free networks, Pareto's law alerts us to distributions that folow power-laws.
How can power-laws be explained? Is some kind of sovereign authority redirecting nature out of a more primordial equality? Barabasi finds that power-laws appear in phase transitions from disorder to order (he draws here from · the Nobel prize-winning work of the physicist Kenneth Wilson). Power-laws "are the patent signatures of self-organization in complex systems" ( 77). Analyzing power-laws on the Web, Barabasi identifes several properties that account for the Web's characteristics as a scale-free network. The first is growth. New sites or nodes are added at a dizzying pace. If new sites decide randomly to link to diferent old sites, old sites will always have an advantage. Just by arriving :first, they will accumulate more links. But growth alone can't account for the power-law degree distribution. A second property is necessa.ryj preferential attachment. New sites have to prefer older, more senior sites. Diferently put, new sites will want to link to those sites that already have a lot of links. They don't link randomly but to the most popular sites which thereby become hubs.
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