The Diversity Paradox revisited: Systemic Effects of Feedback Loops in Recommender Systems

Fuente: arXiv
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Auteurs principaux: Barlacchi, Gabriele, Lalli, Margherita, Ferragina, Emanuele, Giannotti, Fosca, Pedreschi, Dino, Pappalardo, Luca
Format: Preprint
Publié: 2026
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author Barlacchi, Gabriele
Lalli, Margherita
Ferragina, Emanuele
Giannotti, Fosca
Pedreschi, Dino
Pappalardo, Luca
author_facet Barlacchi, Gabriele
Lalli, Margherita
Ferragina, Emanuele
Giannotti, Fosca
Pedreschi, Dino
Pappalardo, Luca
contents Recommender systems shape individual choices through feedback loops in which user behavior and algorithmic recommendations coevolve over time. The systemic effects of these loops remain poorly understood, in part due to unrealistic assumptions in existing simulation studies. We propose a feedback-loop model that captures implicit feedback, periodic retraining, probabilistic adoption of recommendations, and heterogeneous recommender systems. We apply the framework on online retail and music streaming data and analyze systemic effects of the feedback loop. We find that increasing recommender adoption may lead to a progressive diversification of individual consumption, while collective demand is redistributed in model- and domain-dependent ways, often amplifying popularity concentration. Temporal analyses further reveal that apparent increases in individual diversity observed in static evaluations are illusory: when adoption is fixed and time unfolds, individual diversity consistently decreases across all models. Our results highlight the need to move beyond static evaluations and explicitly account for feedback-loop dynamics when designing recommender systems.
format Preprint
id arxiv_https___arxiv_org_abs_2602_16315
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Diversity Paradox revisited: Systemic Effects of Feedback Loops in Recommender Systems
Barlacchi, Gabriele
Lalli, Margherita
Ferragina, Emanuele
Giannotti, Fosca
Pedreschi, Dino
Pappalardo, Luca
Information Retrieval
Artificial Intelligence
Recommender systems shape individual choices through feedback loops in which user behavior and algorithmic recommendations coevolve over time. The systemic effects of these loops remain poorly understood, in part due to unrealistic assumptions in existing simulation studies. We propose a feedback-loop model that captures implicit feedback, periodic retraining, probabilistic adoption of recommendations, and heterogeneous recommender systems. We apply the framework on online retail and music streaming data and analyze systemic effects of the feedback loop. We find that increasing recommender adoption may lead to a progressive diversification of individual consumption, while collective demand is redistributed in model- and domain-dependent ways, often amplifying popularity concentration. Temporal analyses further reveal that apparent increases in individual diversity observed in static evaluations are illusory: when adoption is fixed and time unfolds, individual diversity consistently decreases across all models. Our results highlight the need to move beyond static evaluations and explicitly account for feedback-loop dynamics when designing recommender systems.
title The Diversity Paradox revisited: Systemic Effects of Feedback Loops in Recommender Systems
topic Information Retrieval
Artificial Intelligence
url https://arxiv.org/abs/2602.16315