With most holiday season merchandise already on its way to store shelves, import cargo volume at the nation’s major retail container ports has started to decline for the fall. November traffic is forecast to fall 1.9 percent below its level of a year ago, according to the monthly Global Port Tracker report released today by the National Retail Federation and Hackett Associates.

“As always, retailers are being very strategic with their supply chains,” NRF Vice President for Supply Chain and Customs Policy Jonathan Gold said. “Although sales are expected to be in line with the 10-year average, retailers are keeping inventory levels extremely lean and filling their stores wall-to-wall with discounts and promotions. Unlike in 2008, when the financial crisis caught everyone off-guard, retailers have a strong understanding of the consumer mindset this Christmas.”

U.S. ports followed by Global Port Tracker handled 1.33 million Twenty-foot Equivalent Units in September, the latest month for which after-the-fact numbers are available. That was up 0.4 percent from August and made September the busiest month of the year as retailers rushed to stock stores for the holidays, but was down 0.6 percent from September 2010. One TEU is one 20-foot cargo container or its equivalent.

October was estimated at 1.32 million TEU, down 2.3 percent from a year ago, while November is forecast at 1.21 million TEU, down 1.9 percent from last year, and December is forecast at 1.11 million TEU, down 3.3 percent. After the holidays, January 2012 is forecast at 1.1 million TEU, down 8.7 percent from January 2011; February, traditionally the slowest month of the year, should have only at 996,816 TEU, down 9.4 percent, and March is expected to see 1.08 million TEU, down 0.6 percent.

The total for 2011 is forecast at 14.76 million TEU, just slightly above the 2010 total of 14.75 million TEU.

Global Port Tracker counts only the number of cargo containers imported, not the value of their contents, so cargo volume does not directly correlate with retail sales. NRF is forecasting 2.8 percent growth in holiday sales during November and December over last year, for a total of $465.6 billion.

Despite the year-over-year declines in this month’s report, Hackett Associates founder Ben Hackett cautioned that year-over-year comparisons can be skewed, especially after higher-than-usual numbers in 2010 when cargo patterns changed because of shortages in shipping capacity.

“Months come in four and five week chunks and can give misleading information when looked at in isolation,” Hackett said. “Comparing them on a year-on-year basis is also dangerous as 2010 was such a strong year. We continue to believe that the economy will pick up speed – assuming there is no Euro meltdown – by March or April of next year.”

Global Port Tracker, which is produced for NRF by the consulting firm Hackett Associates, covers the U.S. ports of Long Angeles/Long Beach, Oakland, Seattle and Tacoma on the West Coast; New York/New Jersey, Hampton Roads, Charleston and Savannah on the East Coast, and Houston on the Gulf Coast.