The greatest of the early modern imperial enterprises in terms of physical extent was the joint Hispano-Portuguese monarchy of the period 1580 to 1640. From the last quarter of the sixteenth century onwards then, the idea of an integrated global history based on the existence of worldwide networks of trade, exchange, conquest and circulation can be thought to have at least partly become a reality. The trade between India and Central Asia, or India and East Africa, involved a considerable degree of differentiation and specialization. Europe's share of population was 16 percent in 1400, and over 19 percent four centuries later. The most substantial transformation in the negative direction was caused by the American population collapse of the sixteenth century, with only a partial recovery being evident even as late as 1800, based in part on processes of migration, very largely from Africa and Europe.