Sound statistics are a key component of evidence. However, many institutional, political, and practical barriers impede effective use of data to inform policy. In the fourth paper in this Series on health statistics, we look at the relation between health statistics and policymaking at country and global levels. We propose a fourfold framework to help the transition from data to policy. Good practices include: (1) reconciling statistics from different sources; (2) fostering communication and transparency, including reaching out to the media for dissemination; (3) promoting country ownership of data and statistical analyses; and (4) addressing conflicts of interest, including those arising when workers responsible for attainment of health goals are also charged with measurement and monitoring of progress. Further investments are needed not only in primary data collection across a full range of sources but also in building capacity in countries to analyse, interpret, and present statistics effectively in ways that are meaningful and useful for policymaking.