The years from 1890 to 1930 were politically undistinguished, but saw Brazil rapidly transformed economically and socially by large-scale immigration from Europe and Japan; they were decades of swift growth and swelling cities, which saw a very Brazilian combination of a boom-bust-boom economy and corrupt pork-barrel politics. The boom was led by coffee and rubber , which - at opposite ends of the country - had entirely different labour forces. Millions of nordestinos moved into the Amazon to tap rubber, but the coffee workers swarming into São Paulo in their hundreds of thousands came chiefly from Italy. Between 1890 and 1930 over four million migrants arrived from Europe and another two hundred thousand from Japan. Most went to work on the coffee estates of southern Brazil, but enough remained to turn São Paulo into the fastest-growing city in the Americas. Urban industrialization appeared in Brazil for the first time, taking root in São Paulo to supply the voracious markets of the young cities springing up in the Paulista interior. By 1930, São Paulo had displaced Rio as the leading industrial centre. More improbable was the transformation of Manaus into the largest city of the Amazon. Rubber turned Manaus from a muddy village into a rich trading city within a couple of decades. The peak of the rubber boom , from the 1870s to the outbreak of World War I, financed its metamorphosis into a tropical belle époque outpost, complete with opera house. Rubber exports were second only to coffee, but proved much more vulnerable to competition. Seeds smuggled out of Amazônia by Victorian adventurer Henry Wickham in 1876 ended up in Ceylon and Malaya, where - by 1914 - plantation rubber pushed wild Amazon rubber out of the world markets. The region returned to an isolation it maintained until the late 1950s. Economic growth was not accompanied by political development. Although not all the early presidents were incompetent - Rodrigues Alves (1902-6), for example, rebuilt Rio complete with a public health system, finally eradicating the epidemics that had stunted its growth - the majority were corrupt political bosses, relying on a network of patron-client relationships, whose main ambition seemed to be to bleed the public coffers dry. Power was concentrated in the two most populous states of São Paulo and Minas Gerais, which struck a convenient deal to alternate the presidency between them. This way of ensuring that both sets of snouts could slurp away in the trough uninterrupted was called " café com leite " by its opponents: coffee from São Paulo and milk from the mineiro dairy herds. In fact, it was coffee with milk and sugar: the developing national habit of the sweet cafezinho in the burgeoning cities of the south provided a new domestic market for sugar, which ensured support from the plantation oligarchs of the Northeast. In a pattern that would repeat itself in more modern times, the economy forged ahead while politics went backwards. The saying "Brazil grows in the dark, while politicians sleep" made its first appearance.