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By the early 2000s, the commercial Thoroughbred breeding industry still resembled a relatively broad ecosystem. Elite stallions mattered enormously, but a wide range of sires maintained meaningful market share, regional programs remained viable, and biological limits naturally constrained how dominant any one stallion could become. That landscape has changed dramatically. A review of sire progeny earnings distributions from 2001 through 2025 reveals one of the clearest long-term structural shifts in modern Thoroughbred breeding: an increasingly small number of stallions now account for a growing share of the sport's economic output....