Yachts under port State control: analysis dataset and replication code (Paris MoU, 2015–2026)

Port State control (PSC) research has focused primarily on the commercial merchant fleet, while yacht inspection outcomes remain quantitatively unexplored. We provide, to our knowledge, the first inferential analysis of Paris MoU inspection outcomes for yachts. The comparative design covers 144,042 inspections of 30,603 vessels from February 2015 to July 2026, excluding the structurally incomplete 2017 window, including 2,276 inspections of 774 commercial and pleasure yachts and five conventional segments. A common specification combined negative binomial models for deficiency counts with Firth-penalised logistic models for detention; yacht outcomes were further examined using a hurdle decomposition and vessel-clustered bootstrap inference. Vessel age, associated with 16–60% higher deficiency counts per decade in the comparator segments, showed no comparable monotonic gradient among yachts. Vessel size showed its steepest inverse association in the yacht segment (detention odds ratio 0.58 per doubling of gross tonnage). Grey/Black-listed flag status was associated with positive deficiency burden among yachts (incidence rate ratio 1.49) but not with deficiency occurrence or detention, and attenuated under alternative flag-status assignment. Elevated detention odds under unlisted flags remained a fragile signal warranting monitoring. Pooled interaction tests rejected a common covariate-association structure across segments. These findings suggest that merchant-fleet risk associations may transfer poorly to yachts and support evaluating yacht-specific risk profiling in which vessel size, potentially proxying professional operation, is considered explicitly, alongside transparent assignment of flag-performance status for small registries.