He is best known as a staunch spokesman for free market policies, and for neoliberalism or classical liberalism, as well as for his frequent climate change denial.
In 2005, Hannes organised a regional meeting of the Mont Pelerin Society in Iceland, devoted to "Freedom and Property in the 21st century".
Since 2012, he has been the academic director of RNH, The Icelandic Research Centre for Innovation and Growth, a free-market think tank in Reykjavik.
In 1984, from October 2 to 10, Hannes, with Kjartan Gunnarsson, operated an illegal radio station, to protest against the government monopoly of broadcasting.
But the operation of the station and its closure turned many in the leadership of the Independence Party towards supporting the abolition of the government monopoly.
In early 1990, Hannes published a book on fisheries management, an important subject in Iceland whose main export is fish.
suggesting that Iceland could become an international financial centre offering low corporate taxes and a stable political environment.
The free-market reforms under the reign of the Independence Party 1991–2004 were comprehensive, not only consisting in tax reductions, but also in privatization, liberalization and stabilization.