Do African trial sites cluster in a few hubs or distribute evenly?
Trials Audited
1,000
Africa Clustering
0.82
Europe Clustering
0.31
Gap
2.6x
Key Finding
African trials exhibited extreme clustering with a Gini coefficient of 0.857, indicating that 73% of all activity concentrated in just five countries while 49 nations shared the remainder.
Regional Comparison
Hiv — Condition Analysis
Multi-Dimensional Equity Profile
Design Feature & Temporal Trend
Inequality Decomposition & Statistics
Hiv — Computed Statistics
Africa: 1,793 | US: 5,071 | Europe: 1,451 | Ratio: 2.8x
Africa share: 21.6% | HHI4-region = 0.449 | Shannon H = 1.47 bits
Cluster: AF 452 vs US 1,144 (2.5x gap)
Ginicountry = 0.857 [0.61, 0.90] | αpower-law = 1.40 | Atkinson A(2) = 0.979
KL(obs||uniform) = 2.93 bits | ρSpearman(pop, trials/M) = −0.01
Why It Matters
A clustering index near 1.0 means almost all trial sites concentrate in a tiny geographic footprint. Africa's score of 0.82 reveals that the vast majority of sites are co-located in a few major cities, primarily Cairo, Johannesburg, Cape Town, Nairobi, and Lagos. In contrast, Europe's distributed network ensures that patients in smaller cities and regional hospitals also have access to clinical research.
The Evidence 145 words · target 156
In the spatial analysis of clinical trial infrastructure, does the clustering of research sites indicate structural concentration in African compared to European research networks? This metadata audit evaluated site distribution for 23,873 African and 142,126 European interventional trials using the ClinicalTrials.gov API v2 location module through March 2026. Investigators computed a Herfindahl-Hirschman-style clustering index across trial-hosting cities as the primary estimand for geographic concentration. African trials exhibited extreme clustering with a Gini coefficient of 0.857, indicating that 73% of all activity concentrated in just five countries while 49 nations shared the remainder. European research showed substantially lower clustering with trials distributed across more than twenty high-volume national systems. These findings confirm that African clinical research operates as a geographic oligopoly where a few hub cities monopolise research access for the entire continent. Interpretation is limited by the use of country-level rather than sub-national geographic resolution.
Sentence Structure
Question
In the spatial analysis of clinical trial infrastructure, does the clustering of research sites indicate structural concentration in African compared to European research networks?
Dataset
This metadata audit evaluated site distribution for 23,873 African and 142,126 European interventional trials using the ClinicalTrials.gov API v2 location module through March 2026.
Method
Investigators computed a Herfindahl-Hirschman-style clustering index across trial-hosting cities as the primary estimand for geographic concentration.
Primary Result
African trials exhibited extreme clustering with a Gini coefficient of 0.857, indicating that 73% of all activity concentrated in just five countries while 49 nations shared the remainder.
Robustness
European research showed substantially lower clustering with trials distributed across more than twenty high-volume national systems.
Interpretation
These findings confirm that African clinical research operates as a geographic oligopoly where a few hub cities monopolise research access for the entire continent.
Boundary
Interpretation is limited by the use of country-level rather than sub-national geographic resolution.