Paper
Country involvement changes the hiddenness story because simple country-count buckets blur very different national profiles together.
Which named countries are attached to the quietest older CT.gov studies once country involvement is extracted from recorded trial locations? We analysed 249,507 eligible older closed interventional studies from the March 29, 2026 full-registry snapshot and merged named country lists from the raw locations module. The project explodes country involvement at the study-country level and compares two-year no-results rates, ghost-protocol rates, and visible shares across countries with at least 800 eligible older studies. United States appears in the largest stock at 104,882 eligible older studies and shows a 52.1 percent no-results rate. Egypt is the worst large named country at 95.8 percent no results, China reaches 81.7 percent, while Poland falls to 33.5 percent and Australia to 43.4 percent. Named-country involvement therefore exposes large geographic transparency divides that are hidden by simple country-count buckets alone for large country-linked backlogs. Country labels reflect recorded study locations rather than verified enrollment shares, coordination centers, or country-specific legal duties.