Answer: whether customers of the product would switch to other substitute products marketed by the same firm.
Step-by-step explanation:
Customers regular move from one good to another or from one good to it's substitutes in a process called Customer Migration.
There are various reasons for this such as affordability, change in technology, trends and the like.
When a company contemplates ending a product line and decides to study customer migration patterns, they are checking to see what the customer will switch to when the product is deleted. If they make substitutes to the product to be deleted, they will be checking to see if the customers will switch to these substitutes if the product line is ended.