Money

Money questions are where estimation is most useful and least practised. Nobody has intuition for a trillion, so the method that works is always the same: convert to something human. Divide a national figure by the population, an annual figure by the days in a year, or a total by the people who actually pay it.

The recurring correction in this category is mean against median. Income, wealth, house prices and spending are all right-skewed, so a small number of very large values pull every average above what a typical person experiences. Where both are available, the median is the honest number and the mean is the one that gets quoted.

Prices also need their year. Inflation makes any historical figure meaningless without adjustment, and several questions here turn on exactly that — a 1980s price, a 1970s salary or a nineteenth-century purchase reads completely differently once converted. Every figure on this site is stamped with the year it refers to for that reason.