Abstract
Throughout the world, laws play an important role in shaping population health. Law making is an intervention with measurable effects yet often unfolds without evaluation or monitoring. Policy surveillance-the systematic, scientific collection and analysis of laws of public health significance-can help bridge this gap by capturing important features of law in numeric form in structured longitudinal data sets.Currently deployed primarily in high-income countries, methods for cross-national policy surveillance hold significant promise, particularly given the growing quality and accessibility of global health data. Global policy surveillance can enable comparative research on the implementation and health impact of laws, their spread, and their political determinants. Greater transparency of status and trends in law supports health policy advocacy and promotes public accountability. Collecting, coding, and analyzing laws across countries presents numerous challenges-especially in low-resource settings.With insights from comparative politics and law, we suggest methods to address those challenges. We describe how longitudinal legal data have been used in limited, but important, ways for cross-national analysis and propose incorporating global policy surveillance into core global public health practice.