There was only one, rather limited, official census in this period, in 1901, which returned a population of 736,724. However, the African population was estimated on the basis of hut tax records with a multiplier for the average inhabitants per hut. As no taxes were collected in some areas in the north of the protectorate in 1901, their inhabitants were estimated on the basis of occasional official visits. It is believed that much of the country was reasonably well populated in the mid-19th century, but by the 1880s large areas had become underpopulated through devastating raids by the Ngoni people and the famines which they caused or as the result of slave raiding. There may well have been large areas in the Shire Highlands that had been virtually depopulated.