Séance 5 - Séminaire sur les modèles et méthodes de recherche en sciences économiques

Stéphane Lambrecht, UPHF-LARSH
"A commuter's Turvey diagram: marginal abatement cost curve, optimal pollution and Pigouvian emission fee"

In this paper, we model a commuter's demand for either polluting private vehicule trips or non-polluting public transit trips or a mix of them. This business-as-usual (BAU) optimal solution is then compared with that of a social benevolent planner who takes polluting emissions into account. The commuter's marginal abatement cost function is derived and confronted to the marginal external cost function in order to obtain the optimal polluting emissions. An emission fee is then introduced into the commuter's problem. We derive the Pigouvian level of the emission fee able to decentralize the optimal pollution. These elements constitute the commuter's Turvey diagram and are contrasted with the classical Turvey diagram of a polluting firm. Corner solutions, both for the BAU and the social optimum, are also discussed. The analysis of their decentralization shows specific features due to the fact that the commuter's problem has to be pulled away from the corner in order to reach the social optimum. Finally, an analysis of the value of time at the BAU and at the social optimum is conducted. Decentralizing the social optimum with the emission fee drives the value of leisure time up.