# The 2021 RecSys Challenge Dataset: Fairness is not optional

arXiv: https://arxiv.org/abs/2109.08245 · HTML: https://mlsanity.com/paper/2109.08245/

## Key facts

- Cited by 2 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 16 Sep 2021.

## Built on by (most cited first, 2 of 2)

- [Lessons from the AdKDD'21 Privacy-Preserving ML Challenge](https://mlsanity.com/paper/2201.13123/) (2022)
- [Synerise at RecSys 2021: Twitter user engagement prediction with a fast neural model](https://mlsanity.com/paper/2109.12985/) (2021)

## Abstract (arXiv)

After the success the RecSys 2020 Challenge, we are describing a novel and bigger dataset that was released in conjunction with the ACM RecSys Challenge 2021. This year's dataset is not only bigger (~ 1B data points, a 5 fold increase), but for the first time it take into consideration fairness aspects of the challenge. Unlike many static datsets, a lot of effort went into making sure that the dataset was synced with the Twitter platform: if a user deleted their content, the same content would be promptly removed from the dataset too. In this paper, we introduce the dataset and challenge, highlighting some of the issues that arise when creating recommender systems at Twitter scale.