Here is one reason that President Barack Obama is stumping for more investment in infrastructure to support trade. Exports boost GDP growth. As the chart above shows, exports of goods (the blue part of the bars) and services (red) were a leading source of growth for the U.S. economy early in the recovery, but faded in late 2012 and early 2013. They have rebounded in the two most recent two quarters, contributing 0.6 percentage points to GDP growth in the third quarter and better than a full percentage point in the second quarter. When GDP growth overall is so anaemic, every bit helps.