Maybe people read newer posts instead of (re-)reading older posts
the time of the year (in which reviews occurred)
the length of time open for reviews
the set of users reviews are open to
the set of posts open to review. For example, these are from long ago. (Perhaps if there was a 1 year retrospective, and 2 year, and so on up to 5 years, that could capture engagement earlier, and get ideas for short term and longer term effects.)
some trivial inconveniences around reading the posts to be reviewed (probably already addressed, but did that affect things a lot?)
Other possible factors:
Maybe people read newer posts instead of (re-)reading older posts
the time of the year (in which reviews occurred)
the length of time open for reviews
the set of users reviews are open to
the set of posts open to review. For example, these are from long ago. (Perhaps if there was a 1 year retrospective, and 2 year, and so on up to 5 years, that could capture engagement earlier, and get ideas for short term and longer term effects.)
some trivial inconveniences around reading the posts to be reviewed (probably already addressed, but did that affect things a lot?)
Note that all users can do review. (It’s only voting, and nomination, that’s restricted to highish karma)