Activity on the web can provide more than a snapshot of what people are interested in on a given day. It is also being used, with some success, to predict future stock prices and election results.

Tools such as Google Trends and Blogpulse track what people are talking or thinking about by recording the frequency with which words are entered into search engines and appear on blog sites. Now Peter Gloor at the Massachusetts Institute of Technology is going a step further, and using the web to make specific predictions. His software, called Condor, has predicted the results of an Italian political party's internal election and successfully forecast stock market fluctuations.

Gloor's secret is a property of networks called "betweenness". Condor starts by taking an ordinary search term - the name of a political candidate or a company - and plugging it into ...