citizens. A 2018 survey of public opinion in Switzerland found only 3% considered that joining the EU was a feasible option. The popular initiative entitled "Yes to Europe!", calling for the opening of immediate negotiations for EU membership, was rejected in a 4 March 2001 referendum by 76.8% and all cantons. The Swiss Federal Council, which was in favour of EU membership, had advised the population to vote against this referendum, since the preconditions for the opening of negotiations had not been met. During the history of EU-Swiss relations, the country has undergone several substantial changes in foreign policies, depending on the democratic outcomes of ballot measures. Specific agreements with the EU on freedom of movement for workers and areas concerning tax evasion were first addressed during the Switzerland–EU summit in May 2004 where nine bilateral agreements were signed. Romano Prodi, former President of the European Commission, said the agreements "moved Switzerland closer to Europe." Joseph Deiss of the Swiss Federal Council said, "We might not be at the very centre of Europe but we're definitely at the heart of Europe". He continued, "We're beginning a new era of relations between our two entities." The Swiss population agreed to their country's participation in the Schengen Agreement and joined the area in December 2008. The result of the referendum on extending the freedom of movement of people to Bulgaria and Romania, which joined the EU on 1 January 2007 caused Switzerland to breach its obligations to the EU. The Swiss government declared in September 2009 that bilateral treaties are not solutions and the membership debate has to be examined again while the left-wing Green Party and the Social Democratic Party stated that they would renew their push for EU membership for Switzerland. In the February 2014 Swiss immigration referendum, a federal popular initiative "against mass immigration", Swiss voters narrowly approved measures limiting the freedom of movement of foreign citizens to Switzerland. The European Commission said it would have to examine the implications of the result on EU–Swiss relations. Due to the refusal of Switzerland to grant Croatia free movement of persons, the EU accepted Switzerland's access to the Erasmus+ student mobility program only as a "partner country", as opposed to a "programme country", and the EU froze negotiations on access to the EU electricity market. On 4 March 2016, Switzerland and the EU signed a treaty that extends the agreement on