After 1838, European colonies in the Caribbean with expanding sugar industries imported large numbers of immigrants to meet their acute labor shortage. Large numbers of Jamaicans were recruited to work in Panama and Costa Rica in the 1850s. After slavery was abolished in the United States in 1865, American planters imported temporary workers, called "swallow migrants", to harvest crops on an annual basis. These workers, many of them Jamaicans, returned to their countries after harvest. Between 1881 and the beginning of World War I, the United States recruited over 250,000 workers from the Caribbean, 90,000 of whom were Jamaicans, to work on the Panama Canal. During both world wars, the United States again recruited Jamaican men for service on various American bases in the region. The vast majority of Jamaican Americans are of black Afro-Caribbean descent but there are also some of full or partial Indian Jamaican, Chinese Jamaican, European and Lebanese descent.