The population of London was growing continually throughout the two and a half centuries before the first national census of 1801. Since no census-type listings of inhabitants existed for large areas of the city before 1695, numbers have to be estimated from other sources, principally the bills of mortality. The current opinion about the population of London is indicated by the estimates given in Table 3.1 which are based upon a careful examination of most previous authorities. Nothing is claimed for them other than that they provide a good general guide to the course of population change in London over three centuries, and they show that it was a very large city indeed and that it was growing especially rapidly after 1550. London more than doubled in size during the second half of the sixteenth century, from about 70,000 in 1550 to around 200,000 by 1600. It doubled in size again in the first half of the seventeenth century, from 200,000 in 1600 to 400,000 in 1650. The city's population grew nearly threefold during the seventeenth century, and almost tenfold between the middle of the sixteenth century and the middle of the eighteenth. However, the most rapid changes occurred during the period considered in this book, from 1580 when London numbered just 100,000 inhabitants to 1650 when it contained 400,000 people. This fourfold growth in seventy years was faster than in any other period before modern times.