iOS 6 is already on 15% of iOS devices, even though it was only made available Sept. 19, according to Chitika Insights (www.chitika.com), an advertising and analysis firm.

The research firm took a sample of millions of mobile ad impressions coming out of the Chitika Ad network ranging from Sept. 19 to Sept. 20. The growth rate of iOS 6 was then compared to total iOS Web usage using a time series to illustrate the rate of adoption of the new OS.

Pre-release iOS 6 exhibited low levels of usage due to developer activity. Following its release during the afternoon of Sept. 19, adoption levels soared despite high loads on Apple’s servers, according to Chitika Insights. Yet, within 24 hours, iOS 6 adoption had already reached levels above 15%.

“This level of adoption is a significant development and a testament to the vertical product structure Apple dedicated itself to, particularly when compared to Android’s latest operating system (Jelly Bean) which only saw a 1.5% adoption rate within its first two months,” notes the research firm.