Intellectual property rights in a quality-ladder model with persistent leadership

This paper analyzes the effects of intellectual property rights in a quality-ladder model of endogenous growth in which incumbent firms preemptively innovate in order to keep their position of leadership. Unlike in models with leapfrogging, granting forward protection, and imposing a non-obviousness requirement reduces growth. In the main case where entrants and incumbents have free access to the same R&D technology, infinite protection against imitation, granted independently of the size of the lead, maximizes growth. If entrants have to engage in costly catch up before they can undertake frontier R&D, growth is maximal for a finite (expected) length of protection against imitation.