While the iOS and Android operating systems generate the lion’s share of mobile web traffic in North America, it’s Apple’s iPhone that’s the clear winner. According to a new study by online ad network Chitika, iOS users generated 53.1 percent of web traffic in North America in April, substantially ahead of second place Android, which generated 44.5 percent.

“With several flagship devices upcoming from a number of the largest manufacturers, we expect to observe some subsequent usage share variations between the two operating systems over the next several months, helping to illuminate the overall trend moving into the holiday season,” the report notes.

Chitika points out that it derives its figures by analyzing the overall smartphone usage share figures from the online ad impressions its served between April 1 and April 30, 2014. A typical sample it says is 300 million U.S. and Canadian impressions, measured by page views.

Even though Android smartphones outsell iPhones in terms of unit sales, Android only accounts for 44.5 percent of usage, according to the report. This may suggests that iOS users more broadly use their smartphones for connected tasks, while Android devices are most likely being purchased simply because they are cheaper.

Though not everyone believes this is the case.

“It is hard to imagine that Android buyers would refrain from using the Internet so much less often than other smartphone users, particularly as even poorer users who choose Android for its wide array of low-cost and contract-free phones would still be likely to take advantage of Wi-Fi in ubiquitous public hotspots and their own home network,” notes Electronista. “The more logical conclusion to draw is that the web usage roughly indicates actual North American user share, and thus that Android shipment figures are not a reliable indicator of real-world sales.”