Why is the U.S. share of world merchandise exports shrinking?

As the U.S. share of the world goods trade slips from its level in the 1980s and 1990s, concerns have arisen that the productivity of U.S. exporters has not been growing as fast as that of foreign firms selling similar products. However, an analysis of industry-level trade data suggests that two other factors explain much of the drop in export share: the changing composition of the products traded internationally and the diminished share of U.S. GDP in global output. Declining relative productivity may have played a role in the early 2000s, but it has not been a large factor across industries over the longer term. Overall, there is little evidence of a broad-based decline in the nation?s ability to compete in global markets.