could maintain Brazil only if precious minerals were discovered, Portugal increased its exploratory efforts in the late seventeenth century. As a result, early in the eighteenth century gold and other precious minerals were found. The largest concentration of this gold was in the Southeastern Highlands, mainly in what is now Minas Gerais State. Economy at independence (1822) Despite Brazil's economic troubles, the early nineteenth century was a period of change. First, the Napoleonic Wars forced the Portuguese royal family to flee to Portugal's colony of Brazil in 1808, and for a short period the colony became the seat of the Portuguese empire. Moreover, in 1808 Britain persuaded Portugal to open the colony to trade with the rest of the world, and Portugal rescinded its prohibition against manufacturing (Strangford Treaty). These events paved the way for Brazil's independence on September 7, 1822. Indeed, during this period, the Portuguese royal family and the noblemen who had established themselves in the territory, started many reforms which developed the educational, cultural and economical sectors of Brazil. By 1814, the Portuguese and their allies had defeated Napoleon's armies in the Peninsular War, after had been victorious in the war against the French invasion of Portugal by 1811. However, the King of Portugal remained in Brazil until the Liberal Revolution of 1820, which started in Porto, demanded his return to Lisbon in 1821, but his son Pedro remained in Rio de Janeiro as regent and governor of the newly created Kingdom of Brazil, a Portuguese possession within the new United Kingdom of Portugal, Brazil and the Algarves (1815–22). Brazil's early years as an independent nation were extremely difficult. 1820-1872 for Brazil was a combination of stagnation and regional diversity. According to Leff (1982, 1997), from the time of Brazil's independence in 1822, its rate of GDP growth failed to outpace its population growth. Hence, while the population did expand at a rapid pace (nearly 2 per cent per annum), the country's efforts to improve its performance in per capita terms were largely frustrating until the start of the twentieth century. This protracted and very difficult period of stagnation was, however, the net results of widely varying trends in different regions of the country. The north-eastern part of Brazil, which was a platform for sugar and cotton exports and which accounted for 57 per cent of the country's exports at the start of this period, saw a