Every male Indian between the ages of eighteen and fifty was compelled to pay a certain tribute or poll-tax, for whose collection their chiefs were responsible. About one-sixth of the Indians belonged to estates already granted, and these paid their tribute to the proprietors, the Crown deducting one-fifth. The other five-sixths paid directly to the representatives of the government. In consideration of this tribute, general and indiscriminate personal service was declared to be abolished, but the commutation was not in full. One-seventh of the Indians were required to work for their masters, and the wretched victims of this "mitta" were sent by their caciques to the nearest Spanish town, where they could be engaged by any one who required their services. But these were not all the burdens. The natives of the provinces near the mines were compelled to furnish the labour necessary to work them, and the poor creatures to whose lot it fell to go might never hope to return. Oppressive as was the letter of these laws, their practical application was made infinitely worse by evasions practised with the connivance of the corregidors. Hundreds of Indians were hunted down and carried away to work on farms and in factories under the pretext that the "mitta" returns had not been honestly made, and though the population decreased, the survivors were required to furnish the same number of victims every year. In spite of the slaughter during the civil wars, the Peruvian Indians numbered eight millions in 1575. Including the outlying provinces, the population of the Inca empire must have reached twenty millions in the heyday of its prosperity. Horrible as had been the decrease of the first forty years of Spanish domination, it was a trifle to that which followed the establishment of Toledo's system. In 1573 the impressment for the Potosi mines produced eleven thousand labourers; one hundred years later only sixteen hundred could be found. In the non-mining provinces the destruction was not so stupendous, but some encomiendas, originally containing a thousand adults, were reduced to a hundred within a century, and the miserable survivors were compelled to pay the same sum as had been assessed to their ancestors. The total population of Peru proper had fallen to less than a million and a half within two centuries and that of the whole empire to not more than four millions. So great had been the mortality among the feebler inhabitants of the warm coast valleys that they had practically died out, and their places were taken by negro slaves whose importation began shortly after the conquest.