# Pareto Scaling & Participant Concentration

In power-law economics, does the concentration of participants in a small fraction of trials indicate an extreme Pareto distribution in African clinical research? This analysis applied Pareto scaling models to enrollment data for 23,873 African trials and comparators using ClinicalTrials.gov metadata through March 2026. Africa exhibited an extreme Pareto ratio where an estimated ninety-one percent of all participants were enrolled in just twenty percent of trials, significantly exceeding Europe's sixty-seven percent concentration ratio. The mega-trial model — where a few studies recruit thousands — dominates Africa's research landscape, concentrating risk and benefit in a tiny number of research programmes. The top five percent of African trials by enrollment size accounted for an estimated fifty percent of all continental research participants. These findings demonstrate that Africa's research ecosystem is even more concentrated than the most unequal income distributions. Interpretation is limited by the use of enrollment targets rather than verified participant counts.

## References

1. Alemayehu C, et al. "Behind the mask of the African clinical trials landscape." Trials. 2018;19:519.
2. Drain PK, et al. "Global migration of clinical trials." Nat Rev Drug Discov. 2018;17:765-766.

## Note Block

- Type: research
- App: https://mahmood726-cyber.github.io/africa-e156-students/methods-systems/dashboards/pareto-scaling.html
- Code: https://github.com/mahmood726-cyber/africa-e156-students/blob/master/methods-systems/code/pareto-scaling.py
- Data: ClinicalTrials.gov API v2
- Date: 2026-04-05