World

World questions are the ones where an order of magnitude is the whole answer. Population, land area, production and consumption at planetary scale run to numbers nobody has a feel for, so the skill is not recall but decomposition: take a figure you do know, apply a rate or a share, and check the result per person before trusting it.

Almost every question here can be answered from one anchor — the world holds around eight billion people — plus a per-person rate you can reason about from your own life. How many bananas, cigarettes, cars or litres of water that implies is arithmetic, and arithmetic is far more reliable than memory at this scale.

The recurring trap is generalising from a wealthy country. Most of humanity lives on a fraction of the income a European or American reader assumes, and any global figure estimated from a rich-country sample lands badly wrong. Every number here carries a named source and the year it refers to, because global statistics move and the good ones say so.