Chart of the day: Apple’s iPad and the 13 dwarfs by Philip Elmer-DeWitt @FortuneMagazine June 24, 2013, 4:10 PM EST E-mail Tweet Facebook Google Plus Linkedin Share icons 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.