The Price of Ignorance: Information-Free Quotation for Data Retention in Machine Unlearning

TL;DR

This paper introduces an information-free pricing mechanism for data retention in machine unlearning, achieving near-optimal welfare without knowing users' private preferences, thus addressing privacy and cost concerns under GDPR.

Contribution

It proposes a novel ascending quotation mechanism that operates without private user information, maintaining high welfare and fairness in data deletion scenarios.

Findings

The mechanism achieves at least 99% of the welfare of ideal personalized pricing.

The price of ignorance is near zero, indicating minimal welfare loss.

The mechanism provides noise-robust guarantees and fairness comparable to information-rich benchmarks.

Abstract

When users exercise data deletion rights under the General Data Protection Regulation (GDPR) and similar regulations, mobile network operators face a tradeoff: excessive machine unlearning degrades model accuracy and incurs retraining costs, yet existing pricing mechanisms for data retention require the server to know every user's private privacy and accuracy preferences, which is infeasible under the very regulations that motivate unlearning. We ask: what is the welfare cost of operating without this private information? We design an information-free ascending quotation mechanism where the server broadcasts progressively higher prices and users self-select their data supply, requiring no knowledge of users' parameters. Under complete information, the protocol admits a unique subgame-perfect Nash equilibrium characterized by single-period selling. We formalize the Price of Ignorance -- the welfare gap between optimal personalized pricing (which knows everything) and our information-free quotation (which knows nothing) -- and prove a three-regime efficiency ordering. Numerical evaluation across seven mechanisms and 5000 Monte Carlo runs shows that this price is near zero: the information-free mechanism achieves >=99% of the welfare of its information-intensive benchmarks, while providing noise-robust guarantees and comparable fairness.