The add-on list cannot do it all: a comparative economic evaluation of equity impacts in the German and French inpatient care sectors

As medical innovations become increasingly complex and costly, ensuring equitable access within fiscally constrained health systems is a key policy objective. This study assesses the spatial equity relevance of the Add-on List, a supplementary payment mechanism in the context of Diagnosis-Related Group-Based Financing by examining how regional utilisation patterns of selected high-cost hospital technologies align with equity-relevant structural correlates. The policy is assessed based on its institutional design and the type of technology addressed. A cross-country comparative analysis is conducted between the Add-on List mechanisms in Germany and France. The German model, characterized by intra-budgetary add-on payments, is expected to be associated with less equitable regional utilisation patterns than the extra-budgetary approach adopted in France. Additionally, the Add-on List is expected to be less strongly associated with lower regional inequity for resource-intensive technologies, with the diffusion of specialized healthcare professionals and infrastructure playing a more determinant role. Given differences in institutional objectives and policy logics between German Zusatzentgelte and the French Liste-en-sus, results are interpreted within each national context rather than as a direct effect comparison. Using the Multiple Inequality Index (MII) and applying decomposition analysis at the NUTS 2 level, the study evaluates access disparities for the Stent Retriever, as a resource-intensive technology, and Cetuximab / Panitumumab as a resource-non-intensive technology. Findings are consistent with the interpretation that spatial accessibility correlates are relatively more salient for resource-non-intensive technologies, while infrastructure and specialist diffusion are essential for resource-intensive technologies. We do not identify causal effects of add-on payment design. Findings suggest that more equitable access to resource-non-intensive technologies may be more compatible with the Add-on List context, while complementary investments in infrastructure and specialised human resources may be essential for resource-intensive technologies. Payment mechanisms alone are most likely insufficient to reduce access disparities.