Not all types of memberships are available in all territories or to all customers, and Apple may add or remove membership types and the availability of its services in any territory at any time. Individual and Family Memberships are available in 115 countries while Student Memberships are available in 114 countries. Read here to see a current list of countries for student membership availability.
An additional note that must be made at this phase is: do keep in mind the LTV or the life-time value of your customer here. In certain scenarios (e.g.: subscription-oriented affiliate programs) it makes sense paying significantly higher commissions on the customer’s initial payment to the company when the latter knows that they will make much more (from the same customer) on future payments. More about it later in this text.
The criteria and metrics can be classified according to its type and time span. Regarding the type, we can either evaluate these campaigns "Quantitatively" or "Qualitatively". Quantitative metrics may include "Sales Volume" and "Revenue Increase/Decrease". While qualitative metrics may include the enhanced "Brand awareness, image and health" as well as the "relationship with the customers".