How accurate is your picture of the world, and which facts would you bet on?

Most of us carry an informal picture of the world: how long people live, how many children are in school, how much poverty remains, how wars compare with the past. Hans Rosling's talk "The best stats you've ever seen" is a vivid demonstration of how data can overturn assumptions that feel obvious.

We are asking readers to test their own picture. Pick one global fact you hold confidently, such as how life expectancy or education has changed in your lifetime. Write down what you believe, how confident you are, and where you got the belief. Then check it against a reliable source and tell us what you found.

A good answer would state the original belief, give the confidence level, name the source checked, explain any gap between the two, and say what it changes in how you read the news.

We are not looking for a "gotcha". The point is to practise calibration: knowing how much to trust our own sense of the world.