Robert (Bob) Woods was one of the most eminent historical demographers of his generation. He held the John Rankin Chair of Geography at the University of Liverpool, served as President of the British Society for Population Studies (1991), was founding co-editor (1997-92) of the International Journal of Population Geography and was a recipient of the Society's Murchison Award (1999).

Philip Rees, now an emeritus professor, has spent over half a century at the University of Leeds researching spatial population dynamics, mentoring generations of students, leading programmes for improving access to UK population data, participating in international collaborations and advising government and business. His key contribution, illustrated in the book, has been to show how spatial demographic models, especially those for projecting populations, must be founded on the proper understanding of how migration is measured."