Guess what? People like free upgrades. Specifically, they like it when Apple releases new versions of its OS X operating system for free, as they tend to enjoy higher adoption rates in a shorter amount of time than Apple’s previously paid-for updates.

Also likely helping spur adoption of Apple’s latest OS X iteration, Yosemite, is the fact that Apple treated interested users to an early preview. Yosemite, which Apple dubbed its “best version yet,” was the first of its operating systems to undergo an official public beta test prior to release. According to online ad network Chitika, the beta test gave Yosemite a bit of a boost as far as user installations go.

“To quantify the first week of OS X Yosemite adoption, Chitika Insights sampled tens of millions of U.S. and Canadian Mac OS X-based online ad impressions running through the Chitika Ad Network. The data used within the analysis were drawn from impressions catalogued from October 16 through October 22, 2014,” reads Chitika’s latest blog post(Opens in a new window).

The result? A week after its release, OSX Yosemite enjoys a 12.8 percent adoption rate, according to Chitika. That’s a smidge higher than the 12.4 percent adoption rate that OS X Mavericks hit during the same time period. Both are more than double the adoption rate for Apple’s last paid upgrade, OS X Mountain Lion.

“The day OS X Yosemite was released, more than 1 percent of total North American Mac OS X-based Web traffic was already being generated by users of the new version. This is more than double the North American adoption rate of Mavericks or Mountain Lion going into their respective release dates. However, that advantage was relatively short lived, with both OS X Yosemite and Mavericks posting remarkably similar adoption rates by the end of their respective first post-launch weeks,” reads Chitika’s post.

Prior to the big reveal of Windows 10, there were rumors that Microsoft would take a page from Apple and provide its next-gen OS as a free upgrade. For now, Windows 10 is only available as an early preview version for developers; expect more details next year.

For more, see PCMag’s full review of Yosemite and the slideshow above.