We've been hearing for a while about where Wikipedia's traffic comes from, but here are some new stats from Heather Hopkins at Hitwise on where traffic goes to after visiting Wikipedia. Hopkins had produced some similar stats back in October 2006, and it's interesting to compare the results.
Wikipedia gets plenty of traffic from Google (consistently around half) and indeed other search engines, but what's interesting is that nearly one in ten users go back to Google after visiting Wikipedia, making it the number one downstream destination. Yahoo! is also a popular post-Wikipedia destination.
It was nice to see that Wiktionary and the Wikimedia Commons both make it into the top twenty sites visited by users leaving Wikipedia.
Hopkins also presents a graph illustrating destinations broken down by Hitwise's categories. More than a third of outbound traffic is to sites in the "computers and internet" category, and around a fifth to sites in the "entertainment" category, which probably ties in with the demographics of Wikipedia readers, and the general popularity of pop culture, internet and computing articles on Wikipedia.
Hopkins makes another interesting point on the categories, that large portions of the traffic in each category are to "authority" sites:
"Among Entertainment websites, IMDB and YouTube are authorities. Among Shopping and Classifieds it's Amazon and eBay. Among Music websites it's All Music Guide For Sports it's ESPN. For Finance it's Yahoo! Finance. For Health & Medical it's WebMD and United States National Library of Medicine."
Similarly, Doug Caverly at WebProNews states that the substantial proportion of traffic returning to search engines after visiting Wikipedia "probably indicates that folks are continuing their research elsewhere", and this ties in well with Hopkins' observation about the strong representation of reference sites.
All of this suggests that Wikipedia is being used the way that it is really meant to be used: as a first reference, as a starting point for further research.