Many products—including microprocessors, telecommunications devices, computer software and on-line auction services—make use of multiple technologies, each of which is essential to make or sell the product. The owner of one technology benefits from the existence of complementary...

We examine situations in which a party must make a sunk investment prior to contracting with a second party to purchase an essential complementary input. We study how the resulting old-up problem is affected by the seller’s information about the investing party’s likely returns...

Intellectual property owners often hold the rights to several patents, each of which is essential to make or use a product. We compare the welfare properties of package licenses, under which a licensee pays the same fee regardless of the number of technologies licensed, with component licenses,...

We examine the welfare effects of product-line restrictions, such as those called for by some proponents of network neutrality regulation. We consider a platform that brings together households and application providers. We find that restricting a monopoly platform to a single product has the...