Frei and Duebendorfer collected their data on browsers by analyzing Google's Web logs, which records the user-agent strings of browsers. A user-agent string is data that usually reveals the type of Web browser and version a person uses.

Microsoft's Internet Explorer browser was excluded from some parts of the study since its user-agent string does not reveal incremental version changes for security reasons.

Google's Chrome came out on top. The study found that 97 percent of Chrome users on version 1.x received an upgrade within three weeks. Chrome uses a silent update mechanism where updates are downloaded automatically without user prompts and then applied when the browser is restarted.

Google has also open-sourced its auto-update technology, code-named Omaha, which means anyone can use it. Omaha will poll Google for updates even when Chrome is not running, the researchers wrote. Chrome checks for updates every five hours.

Chrome users may not hit a 100 percent update level due to other problems, such as people not restarting the browser, firewalls blocking updates and some computers, in place such as Internet cafés, that run read-only software images in virtual machines that don't allow software updates, they wrote.