Yanis Varoufakis, former Greek finance minister, listens at the Ambrosetti Forum in Cernobbio, Italy, on Saturday, April 9, 2016. Central banks extraordinary measures to spur growth may eventually show diminishing returns while a key part of the European Central Banks quantitative easing program carries a certain risk that has been mitigated, ECB Executive Board member Yves Mersch said. Photographer: Alessia Pierdomenico/Bloomberg via Getty Images