This study examines the causes of the countercyclicality of the trade balance in the three major sectors of the U.S. economy: services, manufacturing, and agriculture. These results are compared with the results pertinent to the U.S. economy as a whole. At the macroscopic level, Sachs' hypothesis seems to explain the countercyclicality of the trade balance, while results are mixed across individual sectors. The services sector may be explained by Sachs' hypothesis, while results for the manufacturing sector are more consistent with the real business cycle hypothesis. The results for the agricultural sector, however, cannot be explained by either hypothesis.