Aggregation rules range from zero substitutability to full substitutability across dimensions.

Evidence

A good example of a simple best shot rule for teachers would be that if a student gets an A on the final exam, they get an A for the whole course. In terms of substitutability, a good grade on the final substitutes for all the bad grades received during the semester. Teorell et al. use this for part of their measure of democracy: “Since these are considered perfect substitutes (either a directly elected president or a president elected by a directly elected parliament suffices), the index value is arrived at by taking the maximum value of the two” (2019, 78). In short, in the substitutability continuum the weakest link implements no substitutability, while the best shot represents complete substitutability. — Gary Goertz, Social Science Concepts and Measurement, 975

Categorization

• DEFINE: Crisply defines the two poles of the substitutability continuum: weakest link = no substitution, best shot = complete substitution.
• SEED: An essay on how we unconsciously choose aggregation rules — do we grade people by their worst trait or their best?