Imports at the nation’s major retail container ports should see double-digit year-over-year increases for the next two months as a growing economy increases the demand for affordable merchandise, according to the monthly Global Port Tracker report produced by the National Retail Federation and consulting firm Hackett Associates.

“Consumers are spending more freely and retailers are stocking up for the spring and summer seasons,” says Jonathan Gold, NRF’s vice president for supply chain and customs policy. “Merchants are making sure they are prepared to meet growing demand, and imports are essential to providing American families with the products they need at prices they can afford.”

“The threat of a ‘border adjustment’ tax, withdrawal from the Trans-Pacific Partnership and a possible rewrite of the North American Free Trade Agreement might eventually dampen the trading spirit and discourage international trade,” says Ben Hackett, founder of Hackett Associates. “In the meantime, the opposite is happening—trade is continuing to grow despite these developments in Washington.”

Ports covered in the report handled an unusually high 1.67 million twenty-foot equivalent units (TEUs) in January, the latest month for which after-the-fact numbers are available. The large volume came as factories in Asia shipped a surge of products ahead of Lunar New Year shutdowns and was up 6.5% from December and 12.5% year-over-year. One TEU is one 20-foot-long cargo container or its equivalent.

February was estimated at 1.61 million TEUs, up 4.2% from last year. March is forecast at 1.46 million TEUs, up 10.6% from last year; April at 1.59 million TEUs, up 10.1%; May at 1.67 million TEUs, up 2.9%; June at 1.66 million TEUs, up 5.5%, and July at 1.71 million TEUs, up 5.2%.

The first half of 2017 is expected to total 9.7 million TEUs, up 7.4% from the first half of 2016. Cargo volume for 2016 totaled 18.8 million TEUs, up 3.1% from 2015, which had grown 5.4% from 2014.

NRF has forecast that job and income growth coupled with low debt will drive 2017 retail sales—excluding automobiles, gasoline and restaurants—to increase between 3.7% and 4.2% over 2016. Cargo volume does not correlate directly with sales because only the number of containers is counted, not the value of the cargo inside, but nonetheless provides a barometer of retailers’ expectations.

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