Apple's share of holiday sales has seen impressive growth compared to a year ago, according to one report. Analysis firm NPD notes that Apple's control of the market increased sharply from 42 to 57.3 percent within all non-Apple retail stores in the U.S., defying initial worries that the iPod maker's substantial lead would erode in light of waning novelty and the introduction of Microsoft's Zune player. NPD's findings also reveal that the increase has hurt rivals, according to Electronista. Storage firm SanDisk, which surprised industry watchers by usurping all of Apple's longtime challengers to reach second place, fell from 22.1 percent of the holiday 2005 sales to 19.2 this past year. Other competitors are struggling to even approach this smaller number, NPD suggests. Confirming earlier estimates, the Zune captured only 2.8 percent of sales at these same stores in spite of its developer's marketing efforts, and was in fact eclipsed by Creative's largely stagnant 3.4 percent share.