Product Line Rivalry: How Box Office Revenue Cycles Influence Movie Exhibition Variety**

We analyze how product line rivalry by multi-product oligopolists is affected by market size and product substitutability. We show that the width and degree of overlap in competing product lines is determined by the tension between two effects: the drive to “be where the demand is” and the desire to weaken competition and intra-firm product cannibalization. Product lines are shown to be wider and more overlapped in large markets and when product substitutability is weak. We provide econometric support for our main hypotheses using data on weekly film programming choices by first-run movie theatres in a large US metropolitan market