The same charts and the same rules applied to each national register. Which countries take part, and in which panels, is set in the file shared by the twin sites.
Share of dated buildings by construction century (%). Two opposite profiles: France protects mostly the 12th–18th c., Portugal the 16th–20th.
Protection events per decade: France 51,628 events (Mérimée dates field); Portugal: dates extracted from “Decreto/Portaria…” texts by agent reading (4,803 dated classifications).
Share of sacred (religious + funerary) among the century’s dated buildings. Aggregate: France 38.4% · Portugal 39.2% — near twins.
Persons present in BOTH registers (surname + given name). Gustave Eiffel and Oscar Niemeyer built protected heritage on both sides.
Each point = a Getty AAT concept present in BOTH national vocabularies (FR 740 anchored terms, PT 721); axes = share of each register. 130 shared concepts, 49 with ≥10 monuments each side.