Blacks, Hispanics/Latinos, and Native Americans have long been underrepresented in schools and the workplace in science, technology, engineering, and mathematics. Although the monitoring of representation has become a larger and more important enterprise, existing databases make it difficult to discern trends in participation at different stages of science education as well as the "magnitude" of the differences in representation across racial/ethnic groups. We reanalyze four nationally representative databases to call attention to the difficulties, and we offer a solution--a ratio of representation. Our investigation of the representation of students in the biological sciences indicates that gains in the percentages of non-Asian minorities in the biological sciences over almost two decades do not exceed their growth in the U.S. population and, furthermore, that their underrepresentation appears to increase as they move through higher education. We call for the development of multiple measures of representation in the sciences, given the complexities of representing representation and the issue's importance for science, public health, and the American polity. (Contains 9 tables and 7 footnotes.)