One-Way Essential Complements
While competition between ﬁrms producing substitutes is well understood, less is known about rivalry between complementors. We study the interaction between ﬁrms in markets with one-way essential complements. One good is essential to the use of the other but not vice versa, as arises with an operating system and applications. Our interest is in the division of surplus between the two goods and the related incentive for ﬁrms to create complements to an essential good.