Three metrics, summed · a persistence synthesis

Combined Port Persistence
1550 – 1815

Each port's decades in the top ten, summed across all three rankings — ship movements, tonnage and value. A single score for staying power, and a bar that shows which metric carried it.

Composition of the total: Ship movements Tonnage Value Max total = 81  (27 decades × 3 metrics)
#PortShipsTon.Val.TotalComposition (of 81)Breadth

Reading it. The four all-rounders — London (a perfect 81), Amsterdam and Hamburg (78), Lisbon (71) — top every metric. Below them the bar turns telling: specialists ride one or two lenses. Marseille scores 30 with zero tonnage (small coasters); Newcastle, Riga and Königsberg are near-pure tonnage (coal, timber, grain); Batavia, Canton, Havana, Surat and Calcutta live almost entirely in the value column. The breadth dots mark how many of the three metrics each port reached — the truest measure of an all-purpose hub.

Compiled for the Idle Sails project · summed persistence across the ship-count, tonnage and value syntheses, 1550–1815 · a scholarly reconstruction; see the per-metric ledger and sources. Data: research/port-persistence-synthesis.csv.