Growth in the volume of retail shipping imports slowed in the first half of 2017, but the National Retail Federation is still predicting that imports at America's major retail container ports will hit a new high later this summer. Ports covered by the Global Port Tracker handled over 1.6 million Twenty-Foot Equivalent Units in April, up 4.8 percent from March and up 11.3 percent from April 2016. (One Twenty-Foot Equivalent Unit is one 20-foot-long cargo container or its equivalent.) May's total is estimated at almost 1.7 million units, up 3.9 percent from last May, and June is forecast at over 1.6 million units, up 4.1 percent from last year.