Realpolitik, real evidence: what comparative case study methodology teaches us about the policy mixes and political traction needed to reduce health inequalities.

Public health scholarship is shaped by an evidence hierarchy that places systematic reviews of experimental and quasi-experimental studies at the top. This approach is invaluable for isolating the effects of discrete, often downstream interventions. However, it is less suited to evaluating upstream and programmatic efforts to reduce health inequalities at scale, since these methods rarely illuminate how combinations of policies shape inequalities or how such combinations achieve and sustain political and public support. These limitations are not merely technical. Many consequential upstream reforms, such as democratisation, welfare expansion, universal healthcare and fiscal transfers, do not lend themselves to clean treatment-control comparisons and are rarely introduced primarily to reduce health inequalities. In this essay, we outline a complementary comparative case study approach which enables the combined analysis of multiple policies/levers and context-specific circumstances and so identifies the political and policy foundations of reduced health inequalities. We examine four historical episodes in which inequalities narrowed: the United States' Great Society, democratisation and social policy expansion in Brazil, German reunification and England's Health Inequalities Strategy. Across these cases, we identify four recurrent macro-policy packages associated with narrowing inequalities: welfare expansion, improved healthcare access, reductions in income inequality and democratisation. We also examine the political conditions that enabled these packages to be assembled and sustained and the factors that later stalled progress. We conclude by arguing for an evidence agenda that treats policy packages and politics as integral to efforts to improve health equity rather than as residual 'context'.