Q:

Looking for open imbalanced datasets

I'm looking for imbalanced classification datasets to experiment with using synthetic data, ideally with a minor class of less than 10%.  Anyone know specific ones?  Should be open to the public with no limitation of use.  Thanks! 

A:

Most multi-class datasets can be turned into skewed binary classification datasets. 
For example, the default scikit-learn digits dataset contains ~10% 1 and ~90% not-1 images. 
That being said, the UCI Machine Learning Repository hosts many datasets that are skewed, one that's quite skewed is this SMS spam dataset: https://archive.ics.uci.edu/ml/datasets/SMS+Spam+Collection
Another organisation that hosts free but not open datasets is kaggle, one of their datasets that's very skewed is the following:
https://www.kaggle.com/c/jigsaw-toxic-comment-classification-challenge

