From Imperial Spain: 1469-1716, by J. H. Elliott (Penguin, 2002), 2nd ed., Kindle Loc. 4988-5028:
The imperialism of Philip II’s reign had been based on a Spanish-Atlantic economy, in that it was financed out of the resources of America and of a Castile which itself received regular injections of silver from the silver-mines of the New World. During the last decade of the sixteenth century American silver was still reaching Spain in very large quantities, and the port of Seville had an undeniable air of prosperity; but the comforting appearances masked the beginning of a radical change in the structure of the entire Spanish-Atlantic system.
This change was, in part, a direct result of Spain’s war with the Protestant powers of the north. In the first two decades after the outbreak of the Netherlands revolt, the Dutch had continued to trade with the Iberian peninsula. Spain was dependent on northern and eastern Europe for its supplies of grain, timber, and naval stores, a large proportion of which were transported in Dutch vessels. Irked by Spain’s continuing dependence on the Dutch, and anxious to strike a blow at the Dutch economy, Philip II placed an embargo on Dutch ships in Spanish and Portuguese ports in 1585, and again in 1595. The Dutch appreciated as well as Philip II that any interference with their peninsular trade threatened them with disaster. They needed Spanish silver and colonial produce, just as they also needed the salt of Setúbal for their herring industry. Faced with embargoes on their peninsular trade, they therefore reacted in the only possible way, by going direct to the producing areas for the goods they needed – to the Caribbean and Spanish America. From 1594 they were making regular voyages to the Caribbean; in 1599 they seized the salt island of Araya. This intrusion of the Dutch into the Caribbean disrupted the pearl fisheries of Santa Margarita and dislocated the system of maritime communications between Spain’s colonial possessions. For the first time, Spain found itself heavily on the defensive in the western hemisphere, its overseas monopoly threatened by increasingly audacious Dutch and English attacks.
The presence of northern interlopers in the American seas was a serious danger to the Spanish commercial system; but potentially even more serious was the simultaneous transformation in the character of the American economy. During the 1590s the boom conditions of the preceding decades came to an end. The principal reason for the change of economic climate is to be found in a demographic catastrophe. While the white and the mixed population of the New World had continued to grow, the Indian population of Mexico, scourged by terrible epidemics in 1545–6 and again in 1576–9, had shrunk from some 11,000,000 at the time of the conquest in 1519 to little more than 2,000,000 by the end of the century; and it is probable that a similar fate overtook the native population of Peru. The labour force on which the settlers depended was therefore dramatically reduced. In the absence of any significant technological advance, a contracting labour force meant a contracting economy. The great building projects were abruptly halted; it became increasingly difficult to find labour for the mines, especially as the negroes imported to replace the Indians proved to be vulnerable to the same diseases as those which had wiped out the native population; and the problem of feeding the cities could only be met by a drastic agrarian reorganization, which entailed the creation of vast latifundios where Indian labour could be more effectively exploited than in the dwindling Indian villages.
The century that followed the great Indian epidemic of 1576–9 has been called ‘New Spain’s century of depression’ – a century of economic contraction, during the course of which the New World closed in on itself. During this century it had less to offer Europe: less silver, as it became increasingly expensive to work the mines, and fewer opportunities for the emigrants – the 800 or more men and women who were still arriving in the 1590s in each flota from Seville. At the same time, it also came to require less of Europe – or at least of Spain. European luxury products found themselves competing with the products of the Far East carried to America in the Manila galleon. But much more serious from the point of view of Spain was the establishment in its American possessions of an economy dangerously similar to its own. Mexico had developed a coarse cloth industry, and Peru was now producing grain, wine, and oil. These were exactly the products which had bulked so large in the cargoes from Seville during the preceding decades. In fact, the staple Spanish exports to America were ceasing to be indispensable to the settlers, and in 1597 Spanish merchants found it impossible to dispose of all their goods: the American market, the source of Andalusia’s prosperity, was for the first time overstocked.
From the 1590s, therefore, the economies of Spain and of its American possessions began to move apart, while Dutch and English interlopers were squeezing themselves into a widening gap. It was true that Seville still retained its official monopoly of New World trade, and that Sevillan commerce with America reached an all-time record in 1608, to be followed by a further twelve years in which trade figures, while fluctuating, remained at a high level. But, as an index to national prosperity, the figures are deprived of much of their significance by the fact that the cargoes were increasingly of foreign provenance. The goods which Spain produced were not wanted by America; and the goods that America wanted were not produced by Spain.