The comparability of subjective scales

There are long-standing doubts about whether data from subjective scales are cardinally comparable—should we, for instance, believe that if two people self-report their happiness as '7/10' then they are as happy as each other? It is unclear how to assess whether these doubts are justified without first addressing two unresolved theoretical questions: how do people interpret subjective scales, and which assumptions are required for cardinal comparability? This working paper offers answers to both.