Polity’s three democracy categories are arbitrary, driven by symmetry rather than substance.

Evidence

In the case of democracy and using the Polity indicator, because scholars prefer three categories they often divide the spectrum into − 10 to − 5, − 5 to 5, and 5 to 10. As far as I can tell this has never been justified and seems clearly a matter of symmetry, based on no real substantive or semantic considerations. — Gary Goertz, Social Science Concepts and Measurement, 709

Categorization

• QUESTION: Has anyone ever published a substantive rationale for the -5 and +5 cutpoints? Worth chasing in the measurement literature.