The Easterlin paradox is a finding in happiness economics formulated in 1974 by Richard Easterlin, then professor of economics at the University of Pennsylvania, and the first economist to study happiness data.[1] The paradox states that at a point in time happiness varies directly with income both among and within nations, but over time happiness does not trend upward as income continues to grow.[clarification needed] It is the contradiction between the point-of-time and time series findings that is the root of the paradox.[clarification needed] Various theories have been advanced to explain the Paradox, but the Paradox itself is solely an empirical generalization. The existence of the paradox has been strongly disputed by other researchers.