Fixed and mobile broadband; Are they substitutes or complements?

This paper investigates whether fixed and mobile broadband services are substitutes or complements using firm-level panel data obtained from three major telecommunications operators in South Korea. We employ a multi-level demand model based on Hausman et al. (1994), which allow for the possibility of complementarity between differentiated services. The estimated price elasticities of demand indicate that mobile broadband is a (week) substitute for fixed broadband while fixed broadband is complementary to mobile broadband. This is in contrast with the previous studies based on logit models which essentially assume substitution between different technologies. This result implies that fixed and mobile internet services constitute distinctive antitrust markets at least in the early stage of mobile broadband development.