Production of silver for export in Spanish America created large urban centres in mining fields located in barren lands. This offered growing domestic markets for producers of foodstuffs, manufacturing, and services, especially transportation services. These market opportunities pulled communities hitherto dominated by subsistence production into market-oriented production. One of these large mining centres was Potosi in the viceroyalty of Peru. Thirty-five years after the mines there were discovered in 1545, Potosi had 120,000 people in 1580 and 160,000 in 1650 . Two historians have noted that 'the size and influence' of Potosi 'were unparalleled in the Americas and perhaps equal to those of contemporary London' (Burkholder and Johnson, 2004, p. 171). The commercializing effects of the Potosi market covered a regional economy stretching from the Argentine pampa through the central valleys of Chile to coastal Peru and Ecuador (Burkholder and Johnson, op. cit., pp. 171-173). A similar commercializing process provoked by silver mining can be observed in New Spain in the sixteenth and seventeenth centuries (Schell Hoberman, 1991).  
Table 1. Share of export commodities produced by Africans in the Americas, 1501-1850  
| Average annual value of export |  |  |  |
| :-- | :--: | :--: | :--: |
| commodities produced in the Americas | Share produced by Africans |  |  |
| Period | (£000) | Value (£000) | $\%$ |
| $1501-50$ | 1,286 | 694.4 | 54.0 |
| $1551-1600$ | 3,764 | $2,090.6$ | 55.5 |
| $1601-50$ | 6,268 | 4,327 | 69.0 |
| $1651-70$ | 7,970 | $5,504.4$ | 69.1 |
| $1711-60$ | 14,142 | $11,397.5$ | 80.6 |
| $1761-80$ | 21,903 | $18,073.2$ | 82.5 |
| $1781-1800$ | 39,119 | 31,247 | 79.9 |
| $1848-50$ | 89,204 | $61,368.7$ | 68.8 |  
Source: Inikori, J. E. 2002. Africans and the Industrial Revolution in England: A Study in International Trade and Economic Development. Cambridge, Cambridge University Press, table 4.7, p. 197.