Remarking A level papers.
I read an article on this a while back (but I cannot remember where - I just searched and came up empty) but it was by a former marker at AQA. They commented that remarked exams 1/2 the time drop in score (by an average of 8 points), stay the same 1/4 of the time and increase by an average of 2 points for the others. The reason for this skewed data is that the initial markers tend to err on the generous side and on remarking do not.