Population Projections Gone Astray

The BBC has an interesting article that looks at the challenge of making population projections because people don't do what the demographers expect them to do. The article succinctly reports: "Total population change in a country comprises three elements: migration, lifespan and fertility. In no case have people done what they were meant to. The numbers came out and then, drat them, people had the nerve to live even longer, just like that. They had lots of babies and then stopped having lots of babies. Loads suddenly decided to turn up on the doorstep just when it was thought more people might leave." There's also a great graph that shows various population projections in the UK based on different total fertility rates (TFR).