  This paper surveys 60 English Machine Reading Comprehension datasets, with a
view to providing a convenient resource for other researchers interested in
this problem. We categorize the datasets according to their question and answer
form and compare them across various dimensions including size, vocabulary,
data source, method of creation, human performance level, and first question
word. Our analysis reveals that Wikipedia is by far the most common data source
and that there is a relative lack of why, when, and where questions across
datasets.
