Sinologist historians debate the population figures for each era in the Ming dynasty. The historian Timothy Brook notes that the Ming government census figures are dubious since fiscal obligations prompted many families to underreport the number of people in their households and many county officials to underreport the number of households in their jurisdiction. Children were often underreported, especially female children, as shown by skewed population statistics throughout the Ming. Even adult women were underreported; for example, the Daming Prefecture in North Zhili reported a population of 378,167 males and 226,982 females in 1502. The government attempted to revise the census figures using estimates of the expected average number of people in each household, but this did not solve the widespread problem of tax registration. Some part of the gender imbalance may be attributed to the practice of female infanticide. The practice is well documented in China, going back over two thousand years, and it was described as "rampant" and "practiced by almost every family" by contemporary authors. However, the dramatically skewed sex ratios, which many counties reported exceeding 2:1 by 1586, cannot likely be explained by infanticide alone.