Economist Vilfredo Pareto
noticed that 80 percent of wealth was held by 20 percent of the population. Alfred
Lotka found that a few authors write most scientific articles, while many authors write
just one. George Zipf discovered that word frequencies follow the same trend??”a few
words, such as the, are used most often, while others are much rarer. In fact, the power
law is often called Zipf??™s law, and it appears just about everywhere, including mathematics,
physics, economics, and bibliometrics, to name just a few disciplines.
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rank
frequency
1 10 100
Figure 3.6 a typical power-law curve. the item with a rank of 1 occurs many times more often
than the item with rank 10 (similarly with items 10 and 100).
It??™s no surprise then that it occurs in tagging systems as well. One study??”???Complex
Dynamics of Collaborative Tagging??? by Harry Halpin, Valentin Robu, and Hana
Shepherd??”analyzed 500 popular bookmarks from Del.icio.us and found that a powerlaw
curve consistently emerged for each resource.
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