mostSuccessfulHorseYears

Given a predicate that represents a relationship or action between entities, generate a one-sentence description explaining its meaning.  
# Instructions
Focus on describing the relationship, not the entities themselves. 
# Response Format
Begin the description with \' Indicates...\'

Predicate: mostSuccessfulHorseYears

Indicates the years during which a particular horse achieved its highest level of success or best performance relative to other years.