Vertical differentiation and collusion: pruning or proliferation?

In this paper, we tackle the dilemma of pruning versus proliferation in a vertically differentiated oligopoly under the assumption that some firms collude and control both the range of variants for sale and their corresponding prices, likewise a multi-product firm. We analyse whether pruning emerges and, if so, a fighting brand is marketed. We find that it is always more profitable for colluding firms to adopt a pricing strategy such that some variants are withdrawn from the market. Under pruning, these firms commercialize a fighting brand only when facing competitors in a low-end market.