The U.S. container shortage results from reduced imports. As Americans buy less Asian-made goods, fewer containers unload in the United States for use on return routes. But hard-pressed steamship lines exacerbate the crisis, freight forwarders say. Even when a container winds up empty in a big hub such as the Port of Long Beach, ocean carriers are reluctant to spend money sending it to Portland. “They probably could have shipped a lot more hazelnuts earlier than they did this year, but for the availability of containers,” said a Portland freight representative. … Portland export goods are gradually moving up-market, switching from scrap paper, for example, to more valuable cargo such as frozen fruit or vegetables. Ocean carriers charge higher rates for more expensive freight, giving them more incentive to bring empty containers here.