From the beginning of the 2010s, the cohesion of the European Union has been tested by several issues, including a debt crisis in some of the Eurozone countries, increasing migration from Africa and Asia, and the United Kingdom's withdrawal from the EU. A referendum in the UK on its membership of the European Union was held in 2016, with 51.9 per cent of participants voting to leave. The UK formally notified the European Council of its decision to leave on 29 March 2017, initiating the formal withdrawal procedure for leaving the EU; following extensions to the process, the UK left the European Union on 31 January 2020, though most areas of EU law continued to apply to the UK for a transition period which lasted until 23:00 GMT on 31 December 2020.