Rapidly ageing populations and increasing prevalence of chronic diseases present major challenges for policy makers. Populations as well as individuals have different prevalence of conditions related to ageing and chronic disease. This is compounded by cultural and institutional differences in care service provision, eligibility criteria and funding models. Comparing differences at population and individual level helps policy makers address the complexities of maintaining quality in long-term care. This chapter describes how evolution in development of needs assessment instruments has led to a way of producing high-quality data for policy makers. It describes in detail the interRAI system of standardised needs assessment instruments for routine care that generate aggregatable data. Data driven algorithms generate outcome scales, care planning support protocols, quality indicators, and a resource-use casemix system. The chapter then illustrates, with data from nine OECD countries and regions, how needs assessment data recorded at the point of care using the interRAI system can inform policy. It ends with a discussion of factors for consideration when implementing sophisticated needs assessment tools.