The article reports on the inaugural Australian-American system evaluation summit convened in Wyoming, USA, focusing on the application of system evaluation theory (SET). The think tank noted SET’s efficiency principles and published illustrations are emergency response sector specific and pondered whether efficiency measures could be identified for systems targeting complex social problems. The article describes how the think tank used the concept of system waste as a springboard to identify reworks as a universal system efficiency measure. Reworks were defined as repeating all or part of a system standard operating procedure (SOP) or adding additional steps to the SOP to satisfy externalities to the primary purpose. The article then describes the think tank conclusions regarding the utility of reworks as a proxy measure for the four SET factors influencing system efficiency: training, information technology, leadership and culture. The think tank concludes with a discussion of the cautions evaluators should observe when interpreting reworks.