Paper
Country-linked backlog counts do not assign each study to a single nation, but they do show where very old unresolved stock remains concentrated.
Which country-linked CT.gov portfolios still hold the largest stock of studies unresolved at least ten overdue years beyond the two-year reporting mark? We analysed 249,507 eligible older closed interventional studies from the March 29, 2026 full-registry snapshot and exploded country links. We defined ancient backlog as older studies with no posted results and at least ten overdue years beyond the two-year mark, then ranked country-linked portfolios with at least 500 linked studies. The United States led the country-linked table at 22,301 studies, followed by Canada at 4,055, Germany at 3,759, and France at 3,569. Iran had the highest large-country ancient-backlog rate at 46.4 percent, while Norway, India, and Finland also ranked sharply on rate. Ancient backlog shows that very old silence is not restricted to one geography, but remains concentrated in a small set of large country-linked portfolios. Country-linked rows are non-exclusive because multinational studies can contribute to more than one national portfolio in the registry.