Economic development has not kept pace with rapid population growth. This factor, in combination with the prolonged drought, has produced a sizable outflow of emigrants. By the early 1990s there were some 600,000 Cape Verdean emigrants in the US, Europe, Latin America, and other African countries. Some 325,000 were in the US alone—mostly in New England. Remittances to Cape Verde from emigrants enabled many of those who remained in the islands to survive the drought. In 1998, Cape Verde received some 2,000 Bissau Guineans when violence erupted in Guinea Bissau. Of these, about 1,500 left for other countries. At the end of 1998, some 500 refugees remained at two refugee centers, Trinidade and San Jorginho. Between May and August 1999, 500 refugees returned to Guinea Bissau. In 1999, the net migration rate for Cape Verde was -12.35 migrants per 1,000 population.