Interference and spillover effects in recommendation surfaces

Causal Inference
Interference
Spillovers
Recommendation Systems
A project studying how promoting one item affects both that item and nearby competing items when recommendation units interfere.
Published

April 29, 2026

Decision Question

How does promoting one item affect both that item and nearby competing items in the recommendation surface?

Causal Setup

  • Treatment: focal item promotion in simulated recommendation slates.
  • Outcomes: direct item response plus nearby-item displacement or spillover response.
  • Challenge: standard no-interference assumptions do not hold.

Methods

  • Spillover exposure mapping
  • Cluster-randomized estimators
  • Direct, indirect, and total effects
  • Advanced spillover models
  • Sensitivity and final reporting

Portfolio Takeaway

The project makes the portfolio signal that causal claims in ranking and marketplaces must account for displacement, spillovers, and constrained attention.

Selected Figures

25 Final Main Effects

26 Final Direct Indirect Total Decomposition

28 Final Policy Targeting

Notebook Sequence

The links below open rendered HTML versions of the notebooks. The source .ipynb files are kept in the matching folder under notebooks/projects/.

  1. MovieLens Interference Setup and EDA
  2. Spillover Exposure Mapping
  3. Cluster-Randomized Estimators for Direct and Spillover Effects
  4. Direct, Indirect, and Total Effects
  5. Advanced Spillover Models
  6. Sensitivity and Final Report

Generated Artifacts

Limitations

These are notebook-driven causal analyses, not production guarantees. Each project should be read with its identification assumptions, support diagnostics, measurement choices, and sensitivity checks in view.