FRAMINGHAM, Mass. – The handheld device market, already in the throes of unit decline, failed to post a seasonal sequential increase in shipments during the fourth quarter. According to IDC's Worldwide Handheld QView, vendors shipped a total of 683,004 units in the fourth quarter, marking a 53.2% decrease from the same quarter a year ago and a 6.0% decrease from the previous quarter. For the full year, vendors shipped a total of 3.0 million units worldwide, down 44.3% from the 5.5 million units shipped during all of 2006.