Port of Oakland's trade with the world totaled US$21.29bn through the first six months of 2015, a 11.52 percent decrease over its total trade during the same time period last year, according to the analysis published by Trade Numbers.

The analysis of the latest U.S. Census Bureau data shows that exports at this Californian port fell 12.55 percent while imports fell 10.78 percent.

These numbers place the Port of Oakland 26th based on total trade among the 450 U.S. airports, seaports and border crossings through June of 2015. During the same period of 2014 it ranked No. 24. It finished No. 21 in the last full year.

Port of Oakland's top trade partners for the period were China, Japan, South Korea, Taiwan and Germany. Through the same period of the previous year, the top five spots were held by China, Japan, South Korea, Taiwan and Australia, respectively.

Trade with its top trade partner – China – fell 14.05 percent to US$6.82bn. Exports fell 28.15 percent to US$1.18bn, while imports fell 10.38 percent to US$5.64bn.

The port attributed weaker results to labor-management disputes which affected trade growth at most West Coast ports last winter, and a strong dollar which continues to inhibit exports by making U.S. goods more expensive overseas.