
Iavor I. Bojinov
Assistant Professor of Business Administration
Richard Hodgson Fellow
Assistant Professor of Business Administration
Richard Hodgson Fellow


Causal inference is the study of how actions, interventions, or treatments affect outcomes of interest. The methods that have received the lion’s share of attention in the data science literature for establishing causation are variations of randomized experiments. Unfortunately, randomized experiments are not always feasible for a variety of reasons, such as an inability to fully control the treatment assignment, high cost, and potential negative impacts. In such settings, statisticians and econometricians have developed methods for extracting causal estimates from observational (i.e., nonexperimental) data. Data scientists’ adoption of observational study methods for causal inference, however, has been rather slow and concentrated on a few specific applications. In this article, we attempt to catalyze interest in this area by providing case studies of how data scientists used observational studies to deliver valuable insights at LinkedIn. These case studies employ a variety of methods, and we highlight some themes and practical considerations. Drawing on our learnings, we then explain how firms can develop an organizational culture that embraces causal inference by investing in three key components: education, automation, and certification.

The use of online A/B testing has spread rapidly in recent years, fueled by the growing appreciation of its value and the relatively low costs and increasing availability of technology needed to conduct them. Today, it is no exaggeration to say that the successful application of A/B testing is critical to their futures. But many firms often make inadvertent mistakes in how they conduct these experiments. In this article—which employs examples from Netflix and LinkedIn—we offer strategies that companies can adopt to avoid them so they can more effectively spot new opportunities and threats and improve the long-term performance of their businesses.
Iavor Bojinov is an Assistant Professor of Business Administration and the Richard Hodgson Fellow at Harvard Business School. He is the co-PI of the Data Science Operations Lab, and a faculty affiliate in the Department of Statistics at Harvard University and the Harvard Data Science Initiative. His research and writings center on data science operations, aiming to understand how companies should overcome the methodological and operational challenges presented by the novel applications of data science. On the methodological side, he is particularly focused on causal inference from experiments and observational studies in complex settings, such as interference, carry-over effects, and dynamics treatment assignment regimes. His work has been featured in top Statistics, Economics, and Management journals such as Annals of Applied Statistics, Biometrika, the Journal of the American Statistical Association, Quantitative Economics, and Management Science. More broadly, as one of the few scholars that work at the intersection of data science and business, he was the first author to have spotlight featured articles in both the Harvard Business Review and the Harvard Data Science Review.
Professor Bojinov is also the co-creator of the first and second-year MBA course “Data Science for Managers” and has previously taught the “Technology and Operations Management” course. Before joining Harvard Business School, Professor Bojinov worked as a data scientist leading the causal inference effort within the Applied Research Group at LinkedIn. He holds a Ph.D. and an MA in Statistics from Harvard and an MSci in Mathematics from King’s College London.
- Featured Work
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The strength of weak ties is an influential social-scientific theory that stresses the importance of weak associations (e.g., acquaintance versus close friendship) in influencing the transmission of information through social networks. However, causal tests of this paradoxical theory have proved difficult. Rajkumar et al. address the question using multiple large-scale, randomized experiments conducted on LinkedIn’s “People You May Know” algorithm, which recommends connections to users (see the Perspective by Wang and Uzzi). The experiments showed that weak ties increase job transmissions, but only to a point, after which there are diminishing marginal returns to tie weakness. The authors show that the weakest ties had the greatest impact on job mobility, whereas the strongest ties had the least. Together, these results help to resolve the apparent “paradox of weak ties” and provide evidence of the strength of weak ties theory.
Causal inference is the study of how actions, interventions, or treatments affect outcomes of interest. The methods that have received the lion’s share of attention in the data science literature for establishing causation are variations of randomized experiments. Unfortunately, randomized experiments are not always feasible for a variety of reasons, such as an inability to fully control the treatment assignment, high cost, and potential negative impacts. In such settings, statisticians and econometricians have developed methods for extracting causal estimates from observational (i.e., nonexperimental) data. Data scientists’ adoption of observational study methods for causal inference, however, has been rather slow and concentrated on a few specific applications. In this article, we attempt to catalyze interest in this area by providing case studies of how data scientists used observational studies to deliver valuable insights at LinkedIn. These case studies employ a variety of methods, and we highlight some themes and practical considerations. Drawing on our learnings, we then explain how firms can develop an organizational culture that embraces causal inference by investing in three key components: education, automation, and certification.
The use of online A/B testing has spread rapidly in recent years, fueled by the growing appreciation of its value and the relatively low costs and increasing availability of technology needed to conduct them. Today, it is no exaggeration to say that the successful application of A/B testing is critical to their futures. But many firms often make inadvertent mistakes in how they conduct these experiments. In this article—which employs examples from Netflix and LinkedIn—we offer strategies that companies can adopt to avoid them so they can more effectively spot new opportunities and threats and improve the long-term performance of their businesses.
- Journal Articles
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- Rajkumar, Karthik, Guillaume Saint-Jacques, Iavor I. Bojinov, Erik Brynjolfsson, and Sinan Aral. "A Causal Test of the Strength of Weak Ties." Science 377, no. 6612 (September 16, 2022). View Details
- Bojinov, Iavor, and Somit Gupta. "Online Experimentation: Benefits, Operational and Methodological Challenges, and Scaling Guide." Harvard Data Science Review, no. 4.3 (Summer, 2022). View Details
- Bojinov, Iavor I., David Simchi-Levi, and Jinglong Zhao. "Design and Analysis of Switchback Experiments." Management Science (forthcoming). (Pre-published online November 1, 2022.) View Details
- Menchetti, Fiammetta, and Iavor Bojinov. "Estimating the Effectiveness of Permanent Price Reductions for Competing Products Using Multivariate Bayesian Structural Time Series Models." Annals of Applied Statistics 16, no. 1 (March 2022): 414–435. View Details
- Bojinov, Iavor, Ashesh Rambachan, and Neil Shephard. "Panel Experiments and Dynamic Causal Effects: A Finite Population Perspective." Quantitative Economics 12, no. 4 (November 2021): 1171–1196. View Details
- Bojinov, Iavor I., Albert Chen, and Min Liu. "The Importance of Being Causal." Harvard Data Science Review 2.3 (July 30, 2020). View Details
- Bojinov, Iavor I., Guillaume Sait-Jacques, and Martin Tingley. "Avoid the Pitfalls of A/B Testing." Harvard Business Review 98, no. 2 (March–April 2020): 48–53. View Details
- Bojinov, Iavor I., Natesh S. Pillai, and Donald B. Rubin. "Diagnosing Missing Always at Random in Multivariate Data." Biometrika 107, no. 1 (March 2020): 246–253. View Details
- Bojinov, Iavor I., and Neil Shephard. "Time Series Experiments and Causal Estimands: Exact Randomization Tests and Trading." Journal of the American Statistical Association 114, no. 528 (2019): 1665–1682. View Details
- Hollenbach, F.M., I. Bojinov, S. Minhas, N.W. Metternich, M.D. Ward, and A. Volfovsky. "Multiple Imputation Using Gaussian Copulas." Special Issue on New Quantitative Approaches to Studying Social Inequality. Sociological Methods & Research 50, no. 3 (August 2021): 1259–1283. (0049124118799381.) View Details
- Bojinov, Iavor I., and Luke Bornn. "The Pressing Game: Optimal Defensive Disruption in Soccer." Paper presented at the MIT Sloan School of Management, Cambridge, MA, March 2016. View Details
- Working Papers
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- Yue, Daniel, Paul Hamilton, and Iavor Bojinov. "Nailing Prediction: Experimental Evidence on the Value of Tools in Predictive Model Development." Harvard Business School Working Paper, No. 23-029, December 2022. (Revised April 2023.) View Details
- Choudhury, Prithwiraj, Jacqueline N. Lane, and Iavor Bojinov. "Virtual Water Coolers: A Field Experiment on the Role of Virtual Interactions on Organizational Newcomer Performance." Harvard Business School Working Paper, No. 21-125, May 2021. (Revised February 2023.) View Details
- Bojinov, Iavor I., Kevin Wu Han, and Guillaume Basse. "Population Interference in Panel Experiments." Harvard Business School Working Paper, No. 21-100, March 2021. View Details
- Bojinov, Iavor I., David Simchi-Levi, and Jinglong Zhao. "Design and Analysis of Switchback Experiments." Harvard Business School Working Paper, No. 21-034, September 2020. View Details
- Bojinov, Iavor, and Guillaume Basse. "A General Theory of Identification." Harvard Business School Working Paper, No. 20-086, February 2020. View Details
- Cases and Teaching Materials
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- Bojinov, Iavor, Michael Parzen, and Paul Hamilton. "On Ramp to Crypto." Harvard Business School Case 623-040, October 2022. (Revised October 2022.) View Details
- Bojinov, Iavor, Marco Iansiti, and Seth Neel. "Data Privacy in Practice at LinkedIn." Harvard Business School Case 623-024, September 2022. (Revised October 2022.) View Details
- Bojinov, Iavor I., Michael Parzen, and Paul Hamilton. "Causal Inference." Harvard Business School Module Note 622-111, June 2022. (Revised July 2022.) View Details
- Bojinov, Iavor I., Michael Parzen, and Paul Hamilton. "Prediction & Machine Learning." Harvard Business School Module Note 622-101, March 2022. (Revised July 2022.) View Details
- Bojinov, Iavor I., Michael Parzen, and Paul Hamilton. "Linear Regression." Harvard Business School Module Note 622-100, March 2022. (Revised July 2022.) View Details
- Bojinov, Iavor I., Michael Parzen, and Paul Hamilton. "Statistical Inference." Harvard Business School Module Note 622-099, March 2022. (Revised July 2022.) View Details
- Bojinov, Iavor I., Michael Parzen, and Paul Hamilton. "Exploratory Data Analysis." Harvard Business School Module Note 622-098, March 2022. (Revised July 2022.) View Details
- Bojinov, Iavor I., Chiara Farronato, Janice H. Hammond, Michael Parzen, and Paul Hamilton. "Precision Paint Co." Harvard Business School Case 622-055, August 2021. View Details
- Bojinov, Iavor I., and Michael Parzen. "Data Science at the Warriors." Harvard Business School Case 622-048, August 2021. (Revised July 2022.) View Details
- Bojinov, Iavor I., Marco Iansiti, and David Lane. "Orchadio’s First Two Split Experiments." Harvard Business School Case 622-015, August 2021. View Details
- Bojinov, Iavor I., and Karim R. Lakhani. "Experiment B Box Search Implemented." Harvard Business School Multimedia/Video Supplement 621-702, December 2020. View Details
- Bojinov, Iavor I., and Karim R. Lakhani. "Experiment A Box Search." Harvard Business School Multimedia/Video Supplement 621-701, December 2020. View Details
- Choudhury, Prithwiraj, Iavor I. Bojinov, and Emma Salomon. "Creating a Virtual Internship at Goldman Sachs." Harvard Business School Case 621-035, November 2020. View Details
- Bojinov, Iavor I., and Karim R. Lakhani. "Experimentation at Yelp." Harvard Business School Case 621-064, October 2020. (Revised August 2022.) View Details
- Bojinov, Iavor I., Chiara Farronato, Yael Grushka-Cockayne, Willy C. Shih, and Michael W. Toffel. "Comparing Two Groups: Sampling and t-Testing." Harvard Business School Technical Note 621-044, August 2020. View Details
- Research Summary
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My research focuses on overcoming the methodological and operational challenges of developing data science capabilities, what I call data science operations. Today, within leading digital companies, data science is no longer confined to technical teams but is pervasive throughout the entire enterprise. From screening resumes to prioritizing sales leads, algorithms are augmenting or replacing tasks typically done by humans within every business function to achieve unparalleled scale. Traditional organizations are also starting to build data science capabilities and integrate them into their existing operating model to stay competitive. The rapid and widespread permeation of data science, the ability of algorithms to learn causal relationships, and the need for employees and algorithms to work side-by-side have created a host of critical managerial questions that my research in data science operations aims to answer. Data science capabilities can either be deployed externally, providing new products or services (like the Netflix recommendation engine, Google translator, and Uber passenger-driver matching), or internally, augmenting or replacing employee decision-making (like A/B testing, sales prospect rankings, and fraudulent transaction detection). Successful internal data science applications require the correct methodology, technology, processes, and culture to develop the capability. Methodological challenges arise because the statistical theory underpinning modern data science was developed decades ago for applications that are significantly different from the current business use cases. For example, the fundamentals of experimental design were first introduced one hundred years ago for agriculture settings with few experimental units and outcomes; today, companies run hundreds of experiments on millions of connected people, tracking thousands of outcomes. The technology and processes are necessary to transform data scientists from solving specific tasks to developing software platforms that democratize and scale the practice. Finally, developing the right culture to embrace and benefit from data science presents new challenges as it requires humans and algorithms to work together to achieve operational benefits. Data science operations seeks to understand how companies can develop internal data science capabilities by integrating these four components. My research initially focused on how managers can leverage causal inference to help augment innovation and evaluation—a central topic within data science operations. Causal inference methods are categorized as either experimental or non-experimental (referred to as observational studies). Experimentation is now a core capability for most digital firms and conventional companies undergoing a digital transformation. However, the surge in usage has created numerous methodological pitfalls and operational challenges that my research aims to overcome. On the other hand, the adoption of observational studies for decision-making is a more recent trend that was, in part, catalyzed by my article (The Importance of Being Causal) describing how LinkedIn created an observational study software platform. More recently, I've broadened my scope to study the four areas of data science operations: methodology, technology, processes, and culture
- Additional Information
- Areas of Interest
- In The News
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