"The funding of scientific research is almost always justified in terms of the potential for achieving beneficial societal outcomes. In pursuing a particular societal outcome, how can we know if one research portfolio is better than another? In this paper we conceptualize: (1) science in terms of a “supply” of knowledge and information, (2) societal outcomes in terms of a “demand” function that seeks to apply knowledge and information to achieve specific societal goals, and (3) science policy decision-making as a process aimed at “reconciling” the dynamic relationship between “supply” and “demand.” The core of our argument is that “better” science portfolios (that is, portfolios viewed as more likely to advance desired societal outcomes, however defined) would be achieved if science policy decisions reflected knowledge about the supply of science, the demand for science, and the relationship between the two. We provide a general method for pursuing such knowledge, using the specific example of climate change science to illustrate how research on science policy could be organized to support improved decisions about the organization of science itself."