The Treaty of Nice (2001) redefined the qualified majority in terms of a double or even triple majority. While the reweighting of votes works in favour of the large Member States, the qualified majority must also represent a majority of the Member States. This is combined with a system known as the "demographic safety net" which enables each Member State to request verification of whether the qualified majority represents at least 62% of the population of the Union. If this condition is not fulfilled, the decision cannot be adopted.
The Treaty of Lisbon amends the rules of Council voting by introducing a simpler and more transparent system based on the principle of double majority of States and population. The qualified majority can only be reached if it represents at least 55% of the States of the Union and 65% of the European population (Article 16 of the Treaty on European Union and Article 238 of the Treaty on the Functioning of the European Union). This voting system shall only enter into force after a transition period has taken place, ending on 31 October 2014. Until this date, the voting rules in the Treaty of Nice continue to apply.