In this paper I develop indices capturing business/market and nonprofit/mission characteristics of charter schools that can be used to explain many of their observed operational and political choices. This improves on earlier research using only a binary variable classifying charter schools as market or mission rather than letting them take on characteristics of both. Using data from a survey of charter schools, I construct market and mission orientation indices which I then use to reestimate a series of multivariate models published in earlier charter school research that used only the binary distinction between schools. These nuanced, nonmutually exclusive indices reveal aspects of school choices in terms of targeting student populations, recruiting staff, and engaging in political advocacy not uncovered with the original binary distinction. This demonstrates the importance of increasing the sophistication of our empirical measures in the study of charter schools. (Contains 2 tables, 1 figure and 19 notes.)