Deputies, after having voted against the new electoral law proposed by Prime Minister Renzi; at the same time, he announced that he would not renew the PD's membership. In April 2015, Letta moved to Paris to teach at the Sciences Po, a higher education institute of political science. Since 1 September, he became dean of the Paris School of International Affairs (PSIA) of the same institute. Along with his commitment to Sciences Po, he also had teaching periods at the University of Technology Sydney and the School of Global Policy and Strategy at the University of California, San Diego. In the same year, Letta launched Scuola di Politiche (School of Politics), a course of political science for young Italians. In 2016, Letta supported the constitutional reform proposed by Renzi to reduce the powers of the Senate. In the same year, along with the Jacques Delors Institute, he launched a school of political science focused on European issues, known as Académie Notre Europe. In October 2017, he joined the new Comitè Action Publique 2022, a public commission for the reform of state and public administration in France which was strongly supported by President Emmanuel Macron. In March 2019, following the victory of Nicola Zingaretti in the PD leadership election, Letta announced that he would re-join the party after four years. In the same year, Letta also served on the advisory board of the annual Human Development Report of the United Nations Development Programme (UNDP), co-chaired by Thomas Piketty and Tharman Shanmugaratnam. In 2020, he spoke in favour of the constitutional reform to reduce the number of MPs, considering it the first step to overcome perfect bicameralism. Following his retirement from politics, Letta became advisor of many corporations and international organizations like Abertis, where he became member of the Board of Directors in 2016, Amundi, in which he served as member of the Global Advisory Board since 2016, the Eurasia Group, of which he has been Senior Advisor since 2016, Publicis, where he served within the International Advisory Board since 2019 and Tikehau Capital, of which he became member of the International Advisory Board. Letta is a member of many no-profit organizations like the International Gender Champions (IGC), the British Council, Re-Imagine Europa, the Trilateral Commission, in which he presided the European Group, the Aspen Institute Italia, in which he served in the Executive Committee, Associazione Italia ASEAN, of which he became