This week, Travel Today with Peter Greenberg comes from Buenos Aires and the annual World Travel and Tourism Council Global Summit. Joining Peter is Marriott CEO Arne Sorensen, who talks about Marriott's rapid expansion worldwide and the staggering number of hotels they are building daily. Costas Christ, Editor at Large for National Geographic Traveler, speaks about the importance of and a new definition of sustainable travel for post-boomers, millennials and gen-z. And Greg O’Hara, Founder and CEO of Certares, explains how the widening worldwide income gap is affecting the travel industry as well as demand elasticity in travel.  There’s all of this and more as Travel Today with Peter Greenberg comes from the WTTC Annual Global Summit in Buenos Aires, Argentina.