Is the glass half full, half empty, or laced with cyanide? I recently wrote about "statistics, fast and slow" - the gap between the world as we intuitively perceive it, and the world as described in spreadsheets. Nowhere is this gap more obvious than when we are invited to reflect on whether things are going well, or badly.

With some telling exceptions, the situation is this: The world is getting better in many of the ways that matter, but we simply don't realise that this is true. Population growth has slowed dramatically. Most of the world's children have been vaccinated against at least one disease. Girls are rapidly catching up with boys in their access to education. The world is full of flaws, but progress is not only possible - it is happening.