Privacy policies are statements that notify users of the services' data
practices. However, few users are willing to read through policy texts due to
the length and complexity. While automated tools based on machine learning
exist for privacy policy analysis, to achieve high classification accuracy,
classifiers need to be trained on a large labeled dataset. Most existing policy
corpora are labeled by skilled human annotators, requiring significant amount
of labor hours and effort. In this paper, we leverage active learning and
crowdsourcing techniques to develop an automated classification tool named
Calpric (Crowdsourcing Active Learning PRIvacy Policy Classifier), which is
able to perform annotation equivalent to those done by skilled human annotators
with high accuracy while minimizing the labeling cost. Specifically, active
learning allows classifiers to proactively select the most informative segments
to be labeled. On average, our model is able to achieve the same F1 score using
only 62% of the original labeling effort. Calpric's use of active learning also
addresses naturally occurring class imbalance in unlabeled privacy policy
datasets as there are many more statements stating the collection of private
information than stating the absence of collection. By selecting samples from
the minority class for labeling, Calpric automatically creates a more balanced
training set.