Imports at the nation’s major retail container ports saw an unexpected increase during the holiday season, according to data released last week by the National Retail Federation and Hackett Associates. Ports being tracked handled 1.6 million Twenty-Foot Equivalent Units (one 20-foot-long cargo container or its equivalent) in November, the latest month for which after-the-fact numbers are available. That was 11.2 percent higher than in November 2015; Global Port Tracker previously predicted a year-over-year increase of 3.6 percent. December was estimated at 1.5 million Twenty-Foot Equivalent Units, up 7 percent from December 2015, an improvement on the 3.2 percent that had been expected.