Population forecasts shift because demography depends on unpredictable variables

Evidence

Demographics is a notoriously inexact science, whose fluctuations are often dependent on a variety of unpredictable variables, such as lifestyle, economic growth, cultural changes, education on family planning and so on. In 2000, for example, the United Nations revised its population forecasts for the Middle East and the Maghreb in 2025, downwards from a previous estimate of 679 million to 640 million. — Matt Carr, You Are Now Entering Eurabia, 76

Categorization

• XREF: Connects to perennial migration and demographic-panic discourse in Europe and the US.
• QUESTION: Worth checking how many later UN revisions moved in the opposite direction, and by how much.