Chinese literature contains many documents describing classes of society comprised in censuses in the various dynasties. The results of those enumerations have been digested by Ma Twan-lin in a judicious and intelligent manner in the chapters treating on population, from which M. Ed. Biot has elaborated many important data.[150] The early records show that the census was designed to contain only the number of taxable people, excluding all persons bound to give personal service, who were under the control of others. Moreover, all officials and slaves, all persons over 60 or 66 years of age, the weak or sick, those needing help, and sometimes such as were newly placed on state lands, were likewise omitted. Deducting these classes, Ma Twan-lin gives one census taken in the ninth century, B.C., as 13,704,923 persons, between the ages of 15 and 65, living within the frontiers north of the Yangtsz’ River. This figure would be worth, according to the tables of modern statistics, about 65 per cent. of the entire population, or as representing 21,753,528 inhabitants. The mighty conqueror, Tsin Chí Hwangtí, changed the personal corvée to scutage, and introduced a kind of poll-tax, by accepting the money from many who could not be forced to do the work required. This practice was followed in the Han dynasty, and in B.C. 194, the poll-tax was legalized, to include all men between 15 and 66, while a lighter impost was levied on those between 7 and 14. During the four centuries of this family’s régime, the object and modes of a census were well understood. Ma Twan-lin gives the results of ten taken between A.D. 2 and 155. His details show that it was done simply for revenue, and was omitted in bad years, when drought or freshets destroyed the harvests; they show, too, an increase in the number of slaves, that women were now enumerated, and that girls between 15 and 30 paid a poll-tax. In B.C. 30, the limits of age were placed between 7 and 56. The average of these ten censuses is 63,500,600, the first one being as high as 83,640,000, while the next and lowest, taken fifty-five years afterwards, is only 29,180,000, and the third is 47,396,000. These great variations are explained by the disturbances arising in consequence of the usurpation of Wangmang, A.D. 9-27, and subsequent change of the capital, and the impossibility, during this troubled period, of canvassing all parts of the Empire. The inference from these data, that the real population of the Chinese Empire north of the Nan ling at the time of Christ was at least eighty millions, is as well grounded as almost any fact in its history.[151]