8fcb62ec_rics___Introduction___FT_Press__Considerations
[0] 2.7 [Metric] Loyalty [Construction] Measures include share of requirements, willingness to pay premium, willingness to search. [Purpose] Indication of base future revenue stream. [Considerations] 
"Loyalty" itself is not a formal metric, but specific metrics measure aspects of this dynamic. New product entries may alter loyalty levels.
Marketing Metrics: Understanding Market Share and Related Metrics | Introduction | FT Press
Considerations