Nicholas Gregory Mankiw (/ˈmæn.kjuː/; born February 3, 1958) is an American macroeconomist and the Robert M. Beren Professor of Economics at Harvard University. Mankiw is best known in academia for his work on New Keynesian economics. From 2003 to 2005, Mankiw was chairman of the Council of Economic Advisers under President George W. Bush. In 2006, he became an economic adviser to Mitt Romney and continued during Romney's 2012 presidential bid. He is a conservative and he writes a popular blog, ranked the number one economics blog by US economics professors in a 2011 survey. He is also author of the best-selling textbook Principles of Economics. As of April 2015, the IDEAS/RePEc overall ranking put him as the 41st most influential economist in the world; as measured by the h-index, he was ranked the 13th most productive research economist. In 2007 he was elected a member of the American Academy of Arts and Sciences. Along with David Card, he was elected vice president of the American Economic Association for 2014.