The 2012 Global Go To Think Tanks Report and Policy Advice is the most updated source we have (apart from books and academic papers which are published less regularly) to know the evolution of think tanks. It is based in a survey conducted among journalists, experts and institute officials. «The Program’s Rankings remain the first and most comprehensive ranking of the world’s top think tanks, and are based on an annual global peer and expert survey of over 1950 scholars, policymakers, journalists, and regional and subject area experts».