Imports at the nation’s major retail container ports saw an unexpected increase during the industry’s busy holiday season, according to a report released on January 10 by the National Retail Federation.

“We won’t see final sales numbers for a few more days, but import volume suggests that retailers had a strong holiday season,” NRF Vice President for Supply Chain and Customs Policy Jonathan Gold said. “Retailers don’t import merchandise unless they think they can sell it.”

Ports covered by Global Port Tracker handled 1.64 million Twenty-Foot Equivalent Units in November, the latest month for which after-the-fact numbers are available. That was down 1.6% from October since most imported holiday merchandise had already arrived but up 11.2% from November 2015.

The association had previously predicted a year-over-year increase of 3.6%.

December was estimated at 1.54 million TEU, up 7% year-over-year rather than the 3.2% that had been expected.

Cargo volume does not correlate directly to sales because only the number of containers is counted, not the value of the cargo inside, but nonetheless provides a barometer of retailers’ expectations.

NRF’s annual forecast called for $655.8 billion in 2016 holiday sales during November and December, a 3.6 percent increase over 2015. November sales were up 5% year-over-year, and the Commerce Department is scheduled to release December numbers on January 12.

Cargo volume for 2016 is now estimated at 18.8 million TEU, up 2.9% from 2015 rather than the 2% previously expected. Total volume for 2015 was 18.2 million TEU, up 5.4% from 2014.

January is forecast at 1.57 million TEU, up 5.7% from January 2016; February at 1.52 million TEU, down 1.5% from last year; March at 1.41 million TEU, up 6.5%  from last year; April at 1.55 million TEU, up 7.3%, and May at 1.61 million TEU, down 0.5%.