The Ceridian-UCLA Pulse of Commerce Index (PCI) increased a mere 0.3% this March; an indication that while the U.S. economy is still managing to grow, it’s far weaker than what many might think.

“We are moving in the right direction again, but not rapidly enough to offset the declines in trucking that have occurred since last summer,” Edward Leamer, professor of economics and statistics at the UCLA Anderson School of Management, told Fleet Owner.

“The bottom line is that the PCI is suggesting the economy is a lot weaker than many other indicators,” he stressed.

The PCI is based on real-time diesel fuel consumption data by over-the-road trucking operations collected by Ceridian Corp. and then analyzed by economists at UCLA Anderson and Charles River Associates.

By tracking the volume and location of fuel being purchased, the index closely monitors the over the road movement of raw materials, goods-in-process and finished goods to U.S. factories, retailers and consumers.

So far, the PCI reveals economic growth through the first quarter this year is well below that of the fourth quarter of 2011. The 0.3% increase in the PCI this March followed a jump of 0.7% in February, but that wasn’t enough to make up for the 1.7% decline registered in January.

 As a result, the first quarter PCI is below the fourth quarter of last year by 4.9% at an annualized rate, UCLA’s Leamer noted.