Rotationsfairness

Rotationsfairness is a fairness criterion in algorithmic decision making and process design that requires treatment to be invariant under cyclic rotations of positions or options. In systems where items are displayed or assigned in a round-robin or circular order, Rotationsfairness aims to prevent positional advantages by ensuring that no option benefits solely from its fixed position; over time, each option should be exposed to each position with equal frequency.

Formally, consider n positions arranged in a cycle and a policy that assigns outcomes based on position. A policy satisfies Rotationsfairness if, for every rotation by k steps, the distribution of outcomes is identical to that under no rotation. Practically, this can be achieved by ensuring equal exposure across positions over a horizon or by introducing randomized start points or randomized rotations to eliminate systematic position effects.

Applications of Rotationsfairness appear in various domains. In user interfaces and recommender systems, it helps reduce order bias in which items shown earlier receive disproportionately more attention. In sports or tournament scheduling, it mitigates seed or home-field advantages by rotating positions for every round. In resource allocation and load balancing, rotational exposure can distribute wear, access, or priority more evenly across tasks or servers. It also features in experimental design to control for position effects in treatment placement.

Evaluation typically involves exposure and outcome metrics, rotation-invariance tests, and permutation-based analyses to detect deviations from symmetry. Limitations include potential conflicts with efficiency or optimization goals, and the assumption of symmetric positions that may not hold in all contexts.