A theory of class can afford to be subtle. A classification cannot.

A statistical agency has to assign every person in a country to a category, using answers that fit on a form, in a way that is consistent across decades and comparable across countries. The theory has to survive contact with a tick box — which is 7.2.2's operationalisation problem at national scale, and it is where most of what you will ever read about class actually comes from.

The three families of scheme

The problems every scheme has to solve