In the 1990s, patenting schemes changed in many respects: Upcoming new technologies accelerated the shift from price competition towards competition based on technical inventions, a worldwide surge in patenting took place, and the 'patent thicket' arose as a consequence of strategic patenting....

We examine the market power of a seller who repeatedly offers upgraded versions of a product. In the case of pure monopoly, the seller also controls compatibility across versions. In the case of an entrant who offers an upgrade, the incumbent seller also controls subsequent interoperability...

We examine the market power of a seller who repeatedly offers upgraded versions of a product. In the case of pure monopoly, the seller also controls compatibility across versions. In the case of an entrant who offers an upgrade, the incumbent seller also controls subsequent interoperability...