The growth of population
The first census (official count of people) in Britain took place in 1801. After that, there was a census every ten years. For the years before 1801, experts have made estimates. They have studied the records of births and deaths that are kept in churches.
The population of England and Wales began to rise in the mid-eighteenth century. By 1901, it was six times as large as in 1750. The rise was much faster in some places than others. In Lancashire, west Yorkshire, and the west Midlands, the population grew very fast indeed. In other words, it grew fastest in regions where there was a lot of industry.
Historians agree that the population grew. But they do not agree on why it grew. Some say that the main cause was that more babies were born. Some think that the main cause was that people lived longer. Most experts think that it was a mixture of the two. What is clear is that the rise in population took place at the same time as the growth of industry.
Walter Robson: Britain 1750 - 1900; Oxford University Press, 1993, page 44