from the WSJ:
The Commerce Department is expected to say GDP rose at about a 5% annualized pace in the final three months of last year, after inflation, which would be its fastest since early 2006. Slower liquidation of inventories held in warehouses and stockrooms is likely to contribute three percentage points of that growth.
How so? Production collapsed during the recession as companies sold from their existing inventories but didn't order new goods, because of uncertainty about future customer demand. These inventory declines dragged on GDP for six consecutive quarters, the longest streak on record since 1948.
Now that the pace of liquidation is slowing, those changes are showing up as a boost to GDP growth. Some economists prefer to look at final sales to domestic purchasers, a subset of GDP that doesn't include inventories and trade, to better gauge U.S. economic activity. That category is likely to grow at only a 2% pace, similar to the third quarter.
i.e. the inventories went to zero and there was no where to go but up.