The fuel-purchase-based Ceridian-UCLA Pulse of Commerce Index (PCI), rose 0.2% in December after a 0.1% increase in November and a 1.1% increase in October.

Despite the three consecutive months in positive territory, the modest gains weren't enough to offset weakness felt over the past six months.

The December PCI came in 1.2 percent below the June number. On a quarter over quarter basis, the last three months of the year were up over the previous three months at an annualized rate of only 0.5% compared to projected GDP growth of 3 percent.

"Many Wall Street economists have jacked up their 'backcasts' for fourth quarter GDP growth to 3 percent," said Ed Leamer, chief economist for the Ceridian-UCLA Pulse of Commerce Index and Director of the UCLA Anderson Forecast.

The problem is, the PCI index does not support that view.

"The PCI measures inventories destined for factories, stores and homes, and the decline in the PCI in the third quarter correctly anticipated the large negative contribution of inventories to GDP growth," Leamer adds.

With all three months of the fourth quarter now available, the PCI suggests fourth quarter GDP growth of 2.0 percent or less.

"With real retail sales growing more rapidly than the PCI over the last two quarters, however, the first half of 2012 may be an inventory-rebuilding period, allowing inventories to make a substantial contribution to GDP growth," notes Leamer.

PCI is forecasting a 0.29% increase for December Industrial Production when the government estimate is released on January 18.

Ceridian-UCLA Pulse of Commerce Index reports trucking activity in real time by tracking fuel purchase activity from truck stops around the country.

For more information on the PCI index visit