The personal computer industry will experience its worst unit sales decline in the sector's history this year, according to a report from information technology consultant Gartner, Inc. The industry is expected to ship 257 million units in 2009, an 11 percent decline from 2008. The worst previous decline was a 3.2 percent drop in 2001 over 2000. "The PC industry is facing extraordinary conditions as the global economy continues to weaken, users stretch PC lifetimes, and PC suppliers grow increasingly cautious," says George Shiffler, a Gartner research director. The group says both mature and emerging markets will experience sharp declines, although the impact will be stronger in mature markets, where replacements, rather than additions, will account for 80 percent of shipments. The mini-notebook -- or netbook -- market will cushion the blow, with a forecast of 21 million units to ship this year, up from 11.7 million units in 2008.