Import cargo volume at the nation’s major retail container ports is expected to remain at about the same levels as last year through July before starting to resume increases later this summer, according to the monthly Global Port Tracker report released by the National Retail Federation and Hackett Associates.

“With rising gas prices and challenges in the labor and housing markets, consumer spending has slowed and retailers have adjusted their inventory levels accordingly,” NRF Vice President for Supply Chain and Customs Policy Jonathan Gold said. “We are confident long-term consumer demand will grow, and that imports will pick up significantly in the fall.”

U.S. ports followed by Global Port Tracker handled 1.22 million Twenty-foot Equivalent Units in April, the latest month for which numbers are available. That was up 12 percent from March and 7 percent from April 2010. It was the 17th month in a row to show a year-over-year improvement after December 2009 broke a 28-month streak of year-over-year declines. One TEU is one 20-foot cargo container or its equivalent.

May was estimated at 1.27 million TEU, only one-third of 1 percent over May 2010. June is forecast at 1.33 million TEU, a 1 percent increase from a year ago; July at 1.39 million TEU, up one-half of 1 percent from last year; August at 1.47 million TEU, up 3 percent; September at 1.49 million TEU, up 12 percent; and October at 1.54 million TEU, up 19 percent. August through October are traditionally the busiest months of the year as retailers stock up for the holiday season.

The first half of 2011 is forecast at 7.2 million TEU, up 5 percent from the first half of 2010. Global Port Tracker forecasts only six months beyond actual numbers, so a forecast for the full year is not yet available. Imports during 2010 totaled 14.7 million TEU, a 16 percent increase over 2009.

“2011 is turning out to be an uncertain year for shipping,” Hackett Associates founder Ben Hackett said. “The good news for the coming few months is that inventories are too low, which will generate shipping demand as the supply chain moves to re-stock, albeit cautiously.”