In a recent article for “County Cricket Matters” magazine, I looked at the impact of changing counties on a batsman’s average. You can buy it here.
The main conclusion was that a transfer tends to negatively impacts batting.
A surprising observation was that younger players are more adaptable and may improve, while the over thirties rarely benefit from a move. Small sample sizes, so just a tantalising hypothesis for now.
This data covered 2016-2019. The curtailed 2020 season was too short to extend the analysis, so we’ll have to wait for 2021 to see if I’m onto something.
P.S. Much of my analysis considers trends such as these. Since we’ve had two years’ since this blog began, at some point I’ll check if those trends continued. Trends that continue after you’ve noticed them are much more valuable than mere things-that-have-been-true-lately.
Red Ball Data 
Does your impact rating take account of age, so that the maturing of a young player is factored out of his improved raw performance at a new county? Or deterioration in performance of a player past his peak?
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It does take age into account- though I’m aware that not all players age in the same way, so we may just be seeing counties releasing older players who have declined faster than the average bear.
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