PeopleofSuperintelligence

Researcher

Stefan Wager

Stefan Wager is a Stanford researcher whose machine learning methods estimate how treatments affect different people. He earned a mathematics degree at Stanford in 2011 and a statistics PhD in 2016, then worked as a postdoctoral researcher at Columbia in 2016–2017. He coauthored work on causal forests with Susan Athey, generalized random forests with Athey and Julie Tibshirani, and the policytree software paper. The generalized random forests team received the Stanford Open Source Software Prize in 2024. As of October 2026, he is an associate professor at Stanford Graduate School of Business, an associate professor of statistics by courtesy, co-director of the Stanford Causal Science Center, and chief scientist at Lighten.

Now at
Stanford University and Lighten
Works
176
Citations
12,072
h-index
36

Publication numbers from OpenAlex, as of 27 October 2026.

Timeline

  1. 2011

    Mathematics degree at Stanford

    He earns a BS in mathematics at Stanford University in 2011.

  2. 2013

    Understanding dropout training

    In 2013, he coauthors “Dropout Training as Adaptive Regularization” with Sida Wang and Percy Liang. The work explains how dropout controls overfitting in generalized linear models and uses unlabeled data to improve document classification.

  3. 2016–2017

    Statistics doctorate and Columbia postdoc

    He completes a statistics PhD at Stanford in 2016 with Brad Efron and Guenther Walther, writing “Causal Inference with Random Forests.” During the 2016–2017 academic year, he works as a postdoctoral researcher at Columbia University.

  4. 2017

    Joining Stanford Business School

    In 2017, he joins Stanford Graduate School of Business as an assistant professor of operations, information, and technology. He also begins a courtesy appointment as an assistant professor of statistics in Stanford’s School of Humanities and Sciences in 2017.

  5. 2018

    Causal forests with Susan Athey

    In 2018, he and Susan Athey publish their causal forests work in the Journal of the American Statistical Association. The method estimates how treatment effects vary between people and provides confidence intervals for those effects.

  6. 2019

    Generalized random forests

    With Susan Athey and Julie Tibshirani, he publishes “Generalized Random Forests” in the Annals of Statistics in 2019. The method extends random forests to a range of statistical estimation tasks, with an implementation called grf available for R and C++.

  7. 2020

    The policytree software paper

    In 2020, he coauthors the policytree software paper with Erik Sverdrup, Ayush Kanodia, Zhengyuan Zhou, and Susan Athey. Published in the Journal of Open Source Software, the work addresses policy learning with trees.

  8. 2021

    Synthetic difference-in-differences

    In 2021, he coauthors “Synthetic Difference-in-Differences” with Dmitry Arkhangelsky, Susan Athey, David A. Hirshberg, and Guido W. Imbens in the American Economic Review. Their method estimates causal effects from panel data by combining ideas from difference-in-differences and synthetic control.

  9. 2024

    Stanford software prize

    In 2024, he shares the inaugural Stanford Open Source Software Prize with Julie Tibshirani, Susan Athey, and Erik Sverdrup for their generalized random forests software.

  10. As of October 2026

    Stanford professor and Lighten scientist

    As of October 2026, he is an associate professor of operations, information, and technology at Stanford Graduate School of Business and an associate professor of statistics by courtesy. His research connects causal inference, optimization, and statistical learning to problems in statistics, economics, and decision making. He also serves as co-director of the Stanford Causal Science Center and chief scientist at Lighten.

Career

  1. Since 2021Stanford UniversityAssociate Professor of Statistics by Courtesy
  2. NowStanford UniversityAssociate Professor of Operations, Information, and Technology
  3. NowStanford UniversityCo-director of Stanford Causal Science Center
  4. NowLightenChief Scientist
  5. From 2017Stanford UniversityAssistant Professor of Operations, Information, and Technology
  6. 2017–2021Stanford UniversityAssistant Professor of Statistics by Courtesy
  7. 2016–2017Columbia UniversityPostdoctoral Researcher

Education

  1. 2016Stanford UniversityPhD in Statistics
  2. 2011Stanford UniversityBS in Mathematics

From the biography and OpenAlex affiliations (the years of papers that list the organization), so some years are approximate.

Checked career sources: gsb.stanford.edu.

Colleagues

People named in this biography, and people with dated positions at the same organization in the same years.

Sources and credits

Photo: We have no published photo of Stefan Wager yet. Send us a free-licensed photo.

  1. Stefan Wager | Stanford Graduate School of Business gsb.stanford.edu. Checked 27 October 2026.
  2. Dropout Training as Adaptive Regularization proceedings.neurips.cc. Checked 27 October 2026.
  3. Stefan Wager ( Stanford University) | Mathematics and Statistics - McGill University mcgill.ca. Checked 27 October 2026.
  4. Stefan Wager | Department of Statistics statistics.stanford.edu. Checked 27 October 2026.
  5. New Faculty and Electives Enrich Student Experience | Stanford Graduate School of Business gsb.stanford.edu. Checked 27 October 2026.
  6. Estimation and Inference of Heterogeneous Treatment Effects using Random Forests arxiv.org. Checked 27 October 2026.
  7. Generalized Random Forests arxiv.org. Checked 27 October 2026.
  8. Journal of Open Source Software: policytree: Policy learning via doubly robust empirical welfare maximization over trees joss.theoj.org. Checked 27 October 2026.
  9. Synthetic Difference-in-Differences - American Economic Association aeaweb.org. Checked 27 October 2026.
  10. Project team receives first SDS Open Source Software Prize | Department of Statistics statistics.stanford.edu. Checked 27 October 2026.
  11. Stefan Wager web.stanford.edu. Checked 27 October 2026.
  12. About Us | Lighten - Clinical Data Infrastructure & AI lighten-ai.com. Checked 27 October 2026.