The interrelationships among sectors of the U.S. and world economies are many and complex. The food and fiber system is one of the largest sectors of the U.S. economy, accounting for almost 16 percent of gross national product in 1989. The system provides an important example of how events in the U.S. and world economies-from recessions at home and abroad to oil crises-can affect sectors such as farming and inputs. Everything from the weather to Federal policy can mean changes that affect industries that rely on the sector, including farm machinery and financial services.