Measuring Black Sea–Middle Corridor Integration Readiness through a Composite Index and Econometric Evidence

This study develops and applies the Black Sea–Middle Corridor Integration Index (BSMCII), a composite measurement framework for evaluating the integration readiness of the Middle Corridor and the Black Sea basin as a multidimensional multimodal logistics system. Rather than treating the Middle Corridor as a rail-only route or the Black Sea as a peripheral maritime appendix, the study measures corridor readiness through the interaction of port performance, feeder connectivity, transit cost, documentation continuity, reliability, resilience, hinterland integration and green performance. The empirical design uses a calculation-ready and proxy-aware port/route-year dataset covering 19 observations and 11 entities. Eleven Level-I components—DEA, MPI, CPPI, Connectivity, TCDI, CAI, Reliability, Resilience, Hinterland, TradeCost and Green—are aggregated into the BSMCII composite index, quality-adjusted scores and competitive readiness rankings. The framework is then connected to an econometric evidence battery including pooled OLS, WLS, fixed/random-effects diagnostics, gravity-style controls, nonlinear and quantile checks, mediation logic, alternative weights and leave-one-component-out robustness tests. The results show that the Black Sea segment can be measured as a corridor multiplier when feeder services, port productivity, document continuity and hinterland functions are institutionally integrated. Connectivity emerges as the strongest bottleneck, with the lowest component mean, while TradeCost is the second binding constraint. Constanta remains the leading EU Black Sea benchmark, while Varna, Burgas, Poti and TITR form a measurable medium-integration cluster. Poti and Batumi show improvement over the observed period, although Georgian ports still require stronger connectivity, CPPI-type performance, cost predictability, and hinterland integration. Across the strongest model families, BSMCII is positively associated with container/transit flow outcomes, but the study interprets this as association evidence rather than definitive causal identification. The strategic implication is that BTK remains relevant but insufficient as a stand-alone rail logic; the stronger corridor strategy is a Caspian–Black Sea–EU feeder-and-hinterland integration model in which Anaklia becomes transformative only if it improves multiple readiness components simultaneously.