Abstract
In this paper, we develop a theoretical model that enriches the literature on the pros and cons of ownership unbundling vis-A -vis lighter unbundling frameworks in the natural gas markets. For each regulatory framework, we compute equilibrium outcomes when an incumbent firm and a new entrant compete A la Cournot in the final gas market. We find that the entrant's contracting conditions in the upstream market and the transmission tariff are key determinants of the market structure in the downstream gas market (both with ownership and with legal unbundling). We also study how the regulator must optimally set transmission tariffs in each of the two unbundling regimes. We conclude that welfare maximizing tariffs often require free access to the transmission network (in both regulatoy regimes). However, when the regulator aims at promoting the break-even of the regulated transmission system operator, the first-best tariff is unfeasible in both regimes. Hence, we study a more realistic set-up, in which the regulator's action is constrained by the break-even of the regulated firm (the transmission system operator). In this set-up, we find that, for a given transmission tariff, final prices in the downstream market are always higher with ownership unbundling than with legal unbundling.

Abstract

Abstract
This paper examines how firms should allocate their advertising budgets between consumers who have a high preference for their products (i.e., strong segment) and those who prefer competing products (i.e., weak segment). Targeted advertising transmits relevant information to otherwise uninformed consumers and it is used as a price discrimination device. With targeted advertising and price discrimination, we find that, when the attractiveness of the weak segment is low, each firm advertises more intensively in its strong segment. The same result arises when the attractiveness of the weak segment is high and advertising is sufficiently expensive. Interestingly, when the attractiveness of the weak segment is high but advertising costs are sufficiently low, it is optimal for each firm to advertise more intensively in its weak segment. The paper also investigates how advertising strategies and equilibrium profits are affected by price discrimination. Compared with uniform pricing, firms can increase or reduce the intensity of advertising targeted to each segment when price discrimination is allowed. Furthermore, when the attractiveness of the weak market is high, price discrimination boosts firms' profits provided that advertising costs are sufficiently low. The reverse happens when advertising costs are high.

Abstract
This paper studies inefficiencies arising in oligopolies subject to environmental regulation based on tradable emission permits. We propose a duopoly model of upstream-downstream strategic competition: in the permits market a leader sets the price, whereas in the output market Cournot competition occurs. We find that strategic interaction in the output market gives rise to an additional distortion in the permits market where both firms adopt rival's cost-rising' strategies to gain a competitive advantage in the output market. As a result, the price of permits is always higher than firms' marginal abatement costs.

Abstract
A free daily newspaper distributes news to readers and sells ad-space to advertisers, having private information about its audience. For a given number of distributed copies, depending on the type of audience (favorable or unfavorable), the newspaper may either have a large readership or a small readership. A large readership provides a greater return to advertisers, because ads are visualized by more people. A favorable audience has also the advantage of requiring a lower distribution cost (for a given number of distributed copies), because readers are willing to exert more effort to obtain a copy of the free newspaper and are less likely to reject a copy that is handed to them. We find that when the audience is unfavorable, the number of distributed copies and the price of ad-space coincide with those of the perfect information scenario. In contrast, if the audience is favorable, the newspaper prints extra copies to send a credible signal to the advertisers that the audience is favorable. Overprinting is not necessarily welfare-detrimental since readers benefit from the existence of additional copies.

Abstract
There is no consensus on the method to set transmission tariffs for natural gas. The entry-exit system is widely used in European markets because it is cost reflective, it allows the network users to separately book capacity for entry and exit points, beyond its pro-competitiveness characteristics. Some authors, however, defend the adoption of the postage stamp (where a single tariff is charged regardless of the origin of the gas), due to its simplicity. Our goal is to compare these two mechanisms of transmission tariff with respect to the impacts on welfare. We find that the welfare effects crucially depend on the size of the internal market and the fixed costs supported by the incumbent firm. If the domestic market is sufficiently large and there are imports from abroad, consumer surplus is higher under the postage stamp system.