FORTUNE — Based on Web usage, the tablet market in North America still looks like Apple and the 13 dwarfs.
The chart above was posted Monday by Chitika, a mobile ad networks that runs about 4 billion spots per month across 300,000 websites in the U.S. and Canada and — shades of the N.S.A. — collects metadata on some tens of millions of tablet Web impressions.
The charts below show how that usage has changed over the past three months.
Link to the full report: May 2013 Tablet Update.
