Home/American Shipper/NWSA box-volume decline continues in April American ShipperShippingTrade and Compliance NWSA box-volume decline continues in April FreightWaves Staff · Monday, May 21, 2018 Facebook Twitter/X LinkedInThroughput at terminals operated by the Northwest Seaport Alliance slipped another 1.1 percent for the month following a 9.6 percent year-over-year decrease in March. N/A