The knowledge that can be obtained from empirical research in social science ultimately rests on the quantity and quality of measurements of social and economic phenomena. Our research on measurement is complementary to our research on identification. Analysis of identification provides guidance on what is knowable given current data. This stimulates research on measurement methods to improve the information content of data, and thereby expand what is knowable. Our research on identification will identify what types of measurements can expand the frontier of knowledge; our research on measurement focuses on improving methods to obtain those measurements.