How can I determine if two goods are in the same market or market segment? I am not sure how to determine if they have the same demand curve. For example I need to determine if a movie rented from Redbox is or is not in the same market as a movie seen at a Movie Theater. I know both items are related because they deal with the same product movies and I know people rent movies to save money on high movie ticket prices but does that make them be in the same market?