In the seventeenth century the Portuguese imperial economy revolved round sugar, tobacco and salt; in the eighteenth, without completely forsaking its old staples, it came to be based on gold, leather and wine. Its position, pivoted on the great entrepôt of Lisbon, lay somewhere between Anglo-Dutch capitalism, which dominated it in part, and the colonial economies which it was itself shaping and out of which a new national entity, Brazil, was slowly emerging. The dynamics of this profound structural transformation can most rapidly be grasped, and its phases demarcated, if we begin by looking at the course of prices.

Until the peace of 1668 with Spain, some Portuguese prices had been rising gently while others remained stable. The very gradual increase in wheat prices levelled off at Evora from 1667, and in the Azores from 1670, until 1693; and this also happened at Viana do Castelo, though there the prices of rye and maize fell between 1680 and 1693. After 1693, prices in all three markets, as well as in Braganza—in the extreme north, beyond the mountains and isolated from imports—rose to a peak in 1710–11, home-grown cereals ahead of imported. There followed a cyclical decline which reached its lowest point in 1718—three years later in Braganza—and the long-term trend continued very slightly downwards or level until 1740. The price of rice—almost entirely imported, from Valencia, Genoa, Venice—fell in 1680–90, rose to a peak in 1709, then continued to fall until after 1728. What happened to the major export commodities of metro politan Portugal? The price of olive oil in Lisbon, after remaining constant until 1670, went down until about 1692 and then rose steadily to a peak in 1712 (apart from a cyclical depression about 1708, also affecting cereals, though more briefly); after 1712, a really marked downward trend set in until after 1728.