Control of yields is a fundamental tenet of the Appellation Contrôlée system, however sceptical some New World viticulturists are of the concept. The maximum yields cited in the regulations, the rendement maximum autorisé (RA), were almost routinely increased, however, by about 20% throughout the 1970s and 1980s thanks to a frequently used special derogation known as the plafond limite de classement or PLC. In 1993, the INAO announced its intention to curb yields (as the EU has done) but this has not been adopted with noticeable enthusiasm. The PLC has been abolished but it is still possible to request a derogation (up or down) if the application can be justified—by the vintage weather conditions, for example.