IDC revised its global smartphone sales forecast for 2013 upward saying shipments will rise 7.3% as the research firm replaced its original 5.8% prediction after a relatively flat 2012. The firm cited the popularity of cheaper phones and surging demand in developing countries. In the U.S., Apple's iOS operating system gained ground on Android in the second quarter although the Google platform retained a 51% share of the market, according to Kantar Worldpanel ComTech's research. Windows Phone increased its third-place share to 3.5% as BlackBerry fell to 1.2%. Kantar found more than half of cellphone users still own a low-end feature phone.