The mathematical framework underlying the "scenarios" approach for derivate transactions by italian local authorities

The Proposal issued on September, 2009 by the Italian Ministry of Economy and Finance (MEF) for the regulation of derivatives that can be subscribed by Italian local Authorithies outlines the information that should be provided in the contracts in order to assure an approriate level of disclosure. The Proposal has introduced an approch based on so-called “scenarios” requiring the comparison between the corresponding proababilities. We present some comments on the mathematical framework underlying the “scenarios” approach for derivate transactions by Italian local Authorities, showing that it is suited to treat – in a mathematical consistent way – the joint distribution at maturity of the value of the original liability (“portafoglio finanziario iniziale”) and of the liability after the subscription of the derivative by the local Authorithy (“portafoglio strutturato”) only for a very particular set of cases.