Thomas McKeown presents here an explanation of the massive population growth that began around the end of the 17th century and has continued to the present. McKeown's principal focus is Great Britain, but he applies his findings to other areas of the world as well. He writes with greatest confidence about the period since 1838, when regular registration began providing accurate data of the causes of death. However, he has also attempted, with some success, to extrapolate back another 150 years on the basis of piecemeal evidence.
McKeown concludes that by far the most important factor in the population explosion has been the steady decline in mortality from infectious diseases. This resulted chiefly, he believes, from a substantial increase in food supplies during the 18th and 19th centuries, which permitted better nutrition, and from 19th century improvements in public hygiene. He finds that fertility change has not been particularly noteworthy