Also known as covariate shift (shift between training and testing in the distribution of the input variables), see Bickel 2009.

• Bickel et al 2009 - Discriminative Learning Under Covariate Shift
• Duchi 2018 - Learning Models with Uniform Performance via Distributionally Robust Optimization
• Duchi et al 2020 - Distributionally Robust Losses for Latent Covariate Mixtures

• Fairness (Methods that are not robust to distribution shift may not be fair across populations)
• Robustness in NLP