Since the 1930s economists have increasingly emphasized the scientific, quantitative side of their field, which has directed research to topics that can be elaborated through mathematical models. Economist Melvin Reder argues that this ongoing historical shift has been the result of pressure from two directions: from society's demand that expert advice be based on "scientific findings," and from economists themselves, who have wanted to view their own profession as a science. Economics: The Culture of a Controversial Science describes the profession of economics as it has developed in response to these challenges.