Cap and trade system with the objective of cost-optimisation of CO2 reduction efforts. Presently in its third phase 2013-2020. A major revision was laid down in Directive 2009/29/EC. Under this revised EU ETS Directive, a single ETS cap covers the EU Member States and three participating non-EU countries (Norway, Iceland and Liechtenstein), while there are no further individual caps by country. Allowances allocated in the EU ETS from 2013 to 2020 decrease by 1.74% annually, starting from the average level of allowances issued by Member States for the second trading period (2008–2012).