The American Trucking Associations' advanced seasonally adjusted (SA) For-Hire Truck Tonnage Index decreased 1.1% in April after increasing 0.6% in March. (March's gain was more than the preliminary 0.2% increase ATA reported on April 24.) The latest drop put the SA index at 118.7 (2000=100), down from March's level of 120. Compared with April 2011, the SA index was up 3.5%, better than March's 3.1% increase. Year-to-date, compared with the same period last year, tonnage was up 3.8%.

The not seasonally adjusted index, which represents the change in tonnage actually hauled by the fleets before any seasonal adjustment, equaled 116.9 in April, which was 5.5% below the previous month.

'While April's decrease was a little disappointing, the March gain turned out to be stronger than originally thought,' ATA Chief Economist Bob Costello said. 'The ups and downs so far this year are similar to other economic indicators.'

'While just one month, the April's decrease also matches with an economy that is likely to grow slightly slower in the second quarter than in the first quarter,' he said. Costello reiterated last month's noting that the industry should not expect the rate of growth seen over the last couple of years, when tonnage grew 5.8% in both 2010 and 2011. 'I continue to expect tonnage to moderate from the pace over the last two years. Annualized growth in the 3% to 3.9% seems more likely.'

Note on the impact of trucking company failures on the index:Each month, ATA asks its membership the amount of tonnage each carrier hauled, including all types of freight. The indexes are calculated based on those responses. The sample includes an array of trucking companies, ranging from small fleets to multi-billion dollar carriers. When a company in the sample fails, we include its final month of operation and zero it out for the following month, with the assumption that the remaining carriers pick up that freight. As a result, it is close to a net wash and does not end up in a false increase. Nevertheless, some carriers are picking up freight from failures and it may have boosted the index. Due to our correction mentioned above however, it should be limited.

Trucking serves as a barometer of the U.S. economy, representing 67.2% of tonnage carried by all modes of domestic freight transportation, including manufactured and retail goods. Trucks hauled 9 billion tons of freight in 2010. Motor carriers collected $563.4 billion, or 81.2% of total revenue earned by all transport modes.

ATA calculates the tonnage index based on surveys from its membership and has been doing so since the 1970s. This is a preliminary figure and subject to change in the final report issued around the 10th day of the month. The report includes month-to-month and year-over-year results, relevant economic comparisons, and key financial indicators.