Activity at America’s busiest port soared in March. Shipments through the Port of Los Angeles jumped 34% compared the same month last year. It was the biggest year-on-year percentage increase since February 2007. Part of the surge is due to the backlog of shipments slowed down by China’s lunar holiday in February. Asian exports also seem to be bouncing back. And demand is a part of the bounce too, as American consumers awaken from a truly tough winter. Also, some of the gain in Los Angeles might be attributable to slight declines at the nearby port of Long Beach, which saw shipments slip about 2% in March.