Taxe Sur les Transactions Financières : Une Taxe Pigou, Pas Une Taxe Tobin (Tax on Financial Transactions: Why a Pigouvian Tax is More Efficient than a Tobin Tax?)

The European debate around the taxation on financial transactions does not fit in a genuine theoretical framework, therefore exposing the proposed measures to diverse criticisms. What are the foundations of this particular tax? The law proposal of the European Parliament, published in May 2012, states in its first article that "the starting point of this discussion is to transfer some of the costs of the recent crisis to the financial sector," while mentioning at the end of the same paragraph that its aim is to "create additional revenue to finance both the general budget...and the specific policies, especially those related to sustainable development and the fight against climate change." If the aim is to "punish" the banks, one must be able to identify the operations that led to collective costs, so that they constitute the base for the future tax. To what extent a tax on stock exchange transactions (ie. purchase or sale of shares) it is a legitimate response to the production of negative externalities in the financial system? It could be argued that it is even counterproductive, as it does not distinguish the various motivations of financial transactions. On a theoretical level, the approach based on externalities is very robust and constitutes an indisputable foundation for a new taxation in the financial system