60% of institutions exceed the antitrust threshold on AI vendor concentration.
We compute the Herfindahl-Hirschman Index of AI vendor concentration for each institution, applying the standard antitrust measure to AI agent populations rather than to product markets. The U.S. Department of Justice classifies HHI above 1,800 as highly concentrated. Across 542 regulated financial institutions, mean HHI is 2,802, median 2,149. Three hundred and twenty-four sit above the highly concentrated threshold. Nineteen sit at or near 8,000, indicating near-total dependence on a single AI vendor. DORA Article 28 mandates concentration assessment for ICT third parties. The substrate shows the population that fails it.
Each bar groups institutions by their vendor Herfindahl-Hirschman Index, calculated as the sum of squared vendor shares of agent populations. The vertical gold dashed line marks the DOJ "highly concentrated" threshold of 1,800. Bars to the right of the threshold, in navy, count institutions that fail the antitrust threshold for AI vendor concentration. The peak bucket holds 117 institutions between 2,500 and 4,000. The right tail extends to the maximum at 10,000, full single-vendor dependence.