The paper focuses on the innovative French broadband Internet industry that is characterised by inertia phenomena in terms of technology choice. We argue that although inertia on the supply side helps to explain the faster diffusion of ADSL, a more complete picture can be obtained when we consider the existence of costs faced by customers when switching between Internet Service Providers (ISPs). We calculate these so-called "switching costs" and conclude that they act as a barrier to customers' mobility, thus bringing about a dominance of the technology supplied by the largest firm.
