A Difficult Game About Climbing

A mod is compiled against one version of a game. When the game updates, anything that reached into the parts that moved stops working, and it usually stops working silently rather than with a message that explains itself.

That is what the table above counts. It is not a guess: each row is a mod the community has reported as broken by that specific release. The number is a fair measure of how disruptive an update was, and it is the reason people delay updating a game they have modded heavily.