June 11, 2012, 9:57 AM — Who’s tracking your movements across the Web? The biggest offenders are Google and Facebook, says the Evidon Global Tracker Report, a semi-annual analysis of the ad tracking industry that will be made public tomorrow.
Using data collected by its Ghostery browser plug in, Evidon monitored tracking cookies for more than 1.6 million users. The most common tracker, found on more than 70 percent of all sites, is Google Analytics. The second most common tracker is Google Adsense. The rest of the top five is filled out by Facebook’s social plug-ins, Google+ widgets, and Facebook Connect.
The dominance of Google Analytics is no surprise; that free tool is used by tens of millions of Web sites to analyze how many people visited the site, where they came from, how long they stayed, what they looked at, and where they went. It is not generally used to track people across multiple Web sites – which is what’s really driving the controversy around Do Not Track (though Evidon’s report vaguely hints that gAnalytics could be used in this fashion).
The real tracking problem comes from advertising networks that collect information across a wide span of sites, using cookies that are placed on your computer when you load a page containing an ad, and then use your Web surfing history to deliver other ads. Here Google dominates as well, landing in three of the top five slots.
The primary message of this report, in case it isn’t already clear: If you want to worry about somebody tracking you across the Web, worry about Google. And if you have any tracking anxiety left over, apply it to social networks like Facebook, G+, and Twitter.
Other interesting info nuggets contained in the report:
* Facebook, Twitter, and G+ are neck and neck in the race to festoon Web pages with social sharing widgets. On average, users encounter one of these widgets 15 times a day.
* Over 80 percent of Web sites contain five trackers or less (the average is 4.7). But the typical arts and entertainment site (like imdb.com or hulu) contains nearly two dozen, with news and information sites averaging more than 20.
* Every tracker on a site adds to the time it takes for pages to load. The average latency is roughly half a second per tracker, but the worst offenders add more than three seconds per.