Many of the most important pathways by which invasive species enter the country result from the movement of goods in trade. As the largest economy in the world, the U.S. has over 20 of the world’s 30 busiest airports, receives nearly half of all ocean-going vessels each year and admits over 57,000 trucks and 1.1 million visitors daily. Thus, there are ample opportunities for invasive species to enter into the U.S. by land, air or water.