Press
Average market concentration, across 100 markets
76.3%
The share of AI responses naming one of the top 3 companies, averaged across every market measured. Ranges from 52.9% to 90.6% market by market.
See the findings →
The Sierra Index measures how AI assistants answer purchase questions
about local services in the United States — asking OpenAI, Anthropic, Google
Gemini, and Perplexity the same frozen questions, every week, across 100
markets. Raw data and methodology are published in full. We measure. We don't optimize.