To determine adoption levels, Chitika Insights sampled hundreds of millions of North American OS X online ad impressions. They looked at data from June 2 and July 2, 2014 for Yosemite and June 10 and Jul 10, 2013 for Mavericks. The data points were plotted on a three-day rolling average.
In the three days following the release of the first OS X Yosemite Developer Preview, adoption jumped significantly – hitting 0.15% of total U.S. and Canadian Mac OS X Web traffic. That figure is particularly impressive considering that adoption of the OS X Mavericks Developer Preview achieved only a 0.05% share after 30 days. The increased level of aggregate activity for Yosemite is likely partially driven by the prominent changes present in this OS version fueling a higher degree of developer curiosity and experimentation. The changes to Safari in particular may be prompting a greater amount of Web usage from current users in terms of testing and customization.
Chitika expects Yosemite's usage to grow in the short term due to the release of the third Developer Preview on July 7, 2014. Once it's released Yosemite will likely outpace the adoption of any previous Mac desktop operating system.