Simile Raises $200M to Simulate all 8 Billion People on Earth
Simile raises $200M at a $2B valuation to build a foundation model that simulates all 8 billion humans, with Fortune 100 customers already running tens of millions of predictions
- $200M raised: Simile closes a Series B at a $2B valuation led by Greenoaks, just months after a $100M Series A from Index Ventures.
- The mission: Build a foundation model that simulates all 8 billion humans to let enterprises test decisions on synthetic populations before real-world deployment.
- Traction: 5x revenue growth in 5 months, 50+ employees, tens of millions of simulations run for Fortune 100 clients including CVS Health, Deloitte, Gallup, and Wealthfront.
- The science: Agents trained on real human interviews predict behavior with 85% accuracy on the General Social Survey; a confidence model flags reliability per simulation.
- Who built it: CEO Joon Sung Park, creator of Stanford's landmark "Smallville" generative agents paper, co-founded Simile with Stanford professors Michael Bernstein and Percy Liang.
- Key risk: The 85% accuracy benchmark is domain-specific; cross-domain validation and regulatory compliance (EU AI Act, CPPA) remain open challenges as use cases expand into healthcare and finance.
Simile, the Palo Alto-based startup building what it calls "the simulation company," just closed a $200M Series B at a $2 billion post-money valuation. The round was led by Greenoaks, with Index Ventures doubling down and a roster of returning and new investors joining in. The mission, stated plainly on the company blog: simulate all eight billion people on earth, accurately and honestly.
From a Stanford dorm sim to a $2B company in under a year
Joon Sung Park, founder and CEO of Simile, is also the creator of Stanford's "Smallville" generative agents study -- a 2023 research project that placed 25 LLM-driven agents in a Sims-like virtual town. In that paper, the agents woke up, cooked breakfast, went to work, formed opinions, and gossiped. One agent organized a Valentine's Day party; others coordinated invitations and showed up at the right time. The paper won the best paper award at UIST '23.
Park's academic work produced two landmark papers: Social Simulacra (2022), which used GPT-3 to simulate entire subreddits, and Generative Agents (2023), which created that town of 25 AI agents. Park's academic path runs through Swarthmore, UIUC, and a Stanford PhD co-advised by Michael Bernstein (HCI) and Percy Liang (NLP/foundation models). All three are now Simile co-founders, alongside Lainie Yallen.
Since launching just 5 months ago, Simile has grown revenue by 5x, built a new foundation model for human behavior that has run tens of millions of simulations for Fortune 100 enterprises, trained a first-of-its-kind confidence model that predicts the accuracy of every simulation, and expanded from a small home in Palo Alto to a global team of 50+ employees.
The deal terms
- $200M Series B at a $2 billion post-money valuation
- Led by Greenoaks, with returning investors Index Ventures, Hanabi, Bain Capital Ventures, A*, Factory, and CVS Health Ventures, plus new investor Definition
- Capital will be used to accelerate technical training of core human behavior foundation models, expand simulation compute layers, and scale commercial engineering operations across enterprise healthcare, financial services, and media markets