"From approximately three-quarters of a million people in 1760, London continued a strong pattern of growth through the last four decades of the eighteenth century. In 1801, when the first reliable modern census was taken, greater London recorded 1,096,784 souls; rising to a little over 1.4 million inhabitants by 1815" (OldBaileyOnline)I hadn't considered that, but it is quite possible and may well explain why Kent is so inexplicably high in the chart, They were in Holborn in 1800 but born 25 years earlier. Thanks.