PC OEMs need to be ready for a double-digit decline in shipments this year, according to the research from Gartner Inc. The company reports that the PC industry will ship 257 million units in 2009, an 11.9% drop from 2008. Before this decline, PC units experienced their worst decline in 2001, when unit shipments declined 3.2% from 2000 levels.

“The PC industry is facing extraordinary conditions as the global economy continues to weaken,” says George Shiffler, research director at Gartner. Gartner expects both emerging and mature markets to suffer unprecedented market slowdowns. The company expects emerging markets to post a year-over-year decline of 10.4% and a mature-market decline of 13% in 2009.

Gartner reports that worldwide mobile-PC shipments should reach 155.6 million units in 2009, a 9% increase from 2008. Desk-based PC shipments, however, should total 101.4 million units, a 31.9% decrease from 2008. Continued growth in mini-notebook, or netbook, shipments will substantially boost growth in the mobile-PC market. Excluding mini-notebooks, other mobile-PC shipments will grow just 2.7% in 2009, Gartner reports.