  In addition to reproducing discriminatory relationships in the training data,
machine learning systems can also introduce or amplify discriminatory effects.
We refer to this as introduced unfairness, and investigate the conditions under
which it may arise. To this end, we propose introduced total variation as a
measure of introduced unfairness, and establish graphical conditions under
which it may be incentivised to occur. These criteria imply that adding the
sensitive attribute as a feature removes the incentive for introduced variation
under well-behaved loss functions. Additionally, taking a causal perspective,
introduced path-specific effects shed light on the issue of when specific paths
should be considered fair.
