Brazil increased agricultural output about 4,5 percente a year from 1947 to 1965, mainly by expanding the cultivated area, but it has the potential to double the area cultivated. Agricultural production grew more rapidly than population in the 1950's and 1960's, but crop yields remained low and traditional practices were followed with low levels of fertilization. Human labor is the only source of power on three-fourths of the farms. Agricultural output increased rapidly enough to meet rising demands for farm products resulting from population and income growth and to permit some exports. Agriculture has remained the principal economic activity and source of foreign exchange earnings in Brazil with coffee being the major export. The agricultural labor force rose about 2 percent a year, and output per farmworker rose almost as fast.