Imports at the United States' major container ports were projected to grow 7 percent last year over 2016 levels due to improving retail sales throughout 2017 and a strong holiday season, according to the monthly "Global Port Tracker" report published yesterday by the National Retail Federation (NRF) and consultancy Hackett Associates.

The 11 U.S. ports covered by Global Port Tracker handled 1.74 million twenty-foot equivalent units (TEU) in November, the latest month for which after-the-fact numbers were available. Through October, TEU were up 5.8 percent year-over-year. A TEU is one 20-foot-long cargo container or its equivalent.

With December estimated at 1.6 million TEU, the total for 2017 is expected to come to 20.1 million TEU, topping last year's previous record of 18.8 million TEU by 7 percent, according to the report. That would more than double 2016's 3.1 percent increase over 2015 totals.

Last year was marked by an all-time monthly record of 1.8 million TEU, which was set in August. Last year also included five of only seven months on record when imports have hit 1.7 million TEU or higher.

January is forecast at 1.68 million TEU, up 0.2 percent from January 2017; February at 1.62 million TEU, up 12.6 percent from last year; March at 1.5 million TEU, down 2.3 percent; April at 1.66 million TEU, up 3.3 percent, and May at 1.73 million TEU, up 0.4 percent. The February and March percentages are skewed because of annual changes in the timing of the closure of Asian factories for Lunar New Year. This year, Lunar New Year begins Feb. 16.

NRF had forecast 2017 retail sales would grow between 3.2 and 3.8 percent over 2016, and that holiday sales would increase by between 3.6 and 4 percent. Year-end sales figures will be released by the U.S. Census Bureau on Friday. Cargo volume does not correlate directly with sales because the report only counts the number of containers, not the value of its contents. However, TEU activity provides an accurate gauge of retailers' expectations, according to NRF and Hackett.

"On a percentage basis, 2017 was one of the strongest increases we've seen since the end of the Great Recession," Hackett Associates Founder Ben Hackett said in a statement. "That's no minor achievement at a time when many are trying to talk down the economy."

Hackett said TEU activity will slow moderately in 2018. However, he expects continued growth due to continuing high readings in consumer confidence.

Global Port Tracker covers the U.S. ports of Los Angeles/Long Beach, Oakland, Seattle and Tacoma, New York/New Jersey, Hampton Roads, Charleston, Savannah, Port Everglades, Miami, and Houston.