The "ladder of investment" is a regulatory approach proposed by Martin Cave (2006), which has been widely embraced by national regulatory authorities in the European telecommunications sector. The approach entails providing entrants, successively, with different levels of access -the "rungs" of the investment ladder, while inducing them to climb the ladder by setting an access charge that increases over time or by withdrawing access obligations after some pre-determined date (i.e., by setting sunset clauses). Proponents of the ladder of investment approach claim that such regulatory measures would make service-based entry and facility-based entry complementsalbeit they have been traditionally viewed as substitutes-in promoting competition. The regulators, thus, have shown a strong interest in this approach. In this paper, we provide a critical review of the ladder of investment approach by setting out its two underlying assumptions and discussing their validity with references to the related industrial organization literature.

In this paper, we investigate the role of social media as a source of information for recruiters to discriminate applicants. We set up a field experiment over a 12‐month period, involving more than 800 applications from two fictitious applicants which differed in their perceived origins, which is an information available only from their Facebook profiles. During the experiment, an unexpected change in the Facebook layout reduced the salience of the information available on social media profiles. Before this change, a significant 41.7% gap between the two applicants callback rates highlights that personal online profiles are used by recruiters as a source of information to discriminate against applicants of foreign origin. After the layout change that mitigates our signal, the difference in callback rates fades away. This result suggests that the screening conducted by the employers does not go beyond the main pages of profiles. It also illustrates that design choices made by online platforms may have important consequences on the extent of discrimination.

The "ladder of investment" is a regulatory approach proposed by Martin Cave (2006), which has been widely embraced by national regulatory authorities in the European telecommunications sector. The approach entails providing entrants, successively, with different levels of access -the "rungs" of the investment ladder, while inducing them to climb the ladder by setting an access charge that increases over time or by withdrawing access obligations after some pre-determined date (i.e., by setting sunset clauses). Proponents of the ladder of investment approach claim that such regulatory measures would make service-based entry and facility-based entry complementsalbeit they have been traditionally viewed as substitutes-in promoting competition. The regulators, thus, have shown a strong interest in this approach. In this paper, we provide a critical review of the ladder of investment approach by setting out its two underlying assumptions and discussing their validity with references to the related industrial organization literature.