Ştefan-Cosmin Gramatovici — IMO medalist

Data Scientist at OpenAI, working on ChatGPT. Ex Google, Microsoft. Harvard Math 18'

Stefan Gramatovici is a data scientist working on ChatGPT performance as a Member of Technical Staff at OpenAI (Greater Seattle Area). He studied Mathematics at Harvard University (B.A., 2014-2018) and previously worked as a Data Scientist at Google (Chrome Data Science, experimentation and statistical modelling, 2022-2026) and at Microsoft (2018-2022), including the Windows Experimentation Platform and the IDEAs team. In 2016 he interned as a Quantitative Research Intern at Ellington Management Group on automated trading strategies for equities and structured credit products.

Details

LocationGreater Seattle Area

Company siteopenai.com

UniversityHarvard University

Notes

Quant employment verification: CONFIRMED. LinkedIn profile lists a 'Quantitative Research Intern' role at Ellington Management Group (2016) working on automated trading strategies for equities and structured credit products; Ellington Management Group is a registered investment adviser / hedge fund founded 1994 per its own site, so the employer genuinely operates in quantitative finance. This is an internship (May-Aug 2016 per caller lead), not full-time, and it rests on index/LinkedIn data rather than a separate primary-source employment record.Jun 1, 2016
Identity anchor: official IMO record confirms Ştefan-Cosmin Gramatovici represented Romania at IMO 2013 with a bronze medal (rank 211, 17 points).Jul 1, 2013
LinkedIn/index profile shows 'Stefan Gramatovici', Harvard Mathematics class of 2018, now Member of Technical Staff at OpenAI in Greater Seattle; the Romanian name plus Harvard-math timeline is consistent with the IMO 2013 Romanian contestant, but no single source yet directly joins the two identities.Sep 1, 2026
Career timeline (index/LinkedIn-sourced): OpenAI Member of Technical Staff (2026-), Google Data Scientist Research (2022-2026), Microsoft Data Scientist II (2020-2022), Microsoft Data Scientist (2018-2020), Microsoft Data Science Intern (2017), Ellington quant research intern (2016).Sep 1, 2026
Co-authored 'Novelty and Primacy: A Long-Term Estimator for Online Experiments' (arXiv 2102.12893) on long-term effects in online experiments while at Microsoft.Feb 1, 2021

Experience

Member of Technical Staff at OpenAI

Data Science for ChatGPT performance.

Data Scientist, Research at Google

Greater Seattle Area

Working in Chrome Data Science on experimentation and advanced statistical modelling.

Data Scientist II at Microsoft

Redmond, Washington, United States

IDEAs team: Built a hierarchical forecasting model for business time series such as number of M365 Subscribers. Advised on experiment best practices. CosmosDB: Developed a new heur

Data Scientist at Microsoft

Worked on WExp, the Windows Experimentation Platform. Built model to identify and estimate long term effects in experiments. See https://arxiv.org/abs/2102.12893

Data Science Intern at Microsoft

Redmond, Washington

Build a prototype differential privacy library. It allows querying of customer data with managed privacy loss under the server-side differential privacy model.

Quantitative Research Intern at Ellington Management Group

Greater New York City Area

Quantitative Research Intern working on automated trading strategies for equities and structured credit products

Education

Harvard University

Bachelor's degree, Mathematics

AchievementsBronze medal, International Mathematical Olympiad (IMO) 2013, representing Romania; rank 211, 17 points

Articles

arxiv.org/abs/2102.12893

tandfonline.com/doi/abs/10.1080/00401706.2022.2124309