Inspired by this post on reddit, I decided to write a little program to visualize and analyze the pgn data provided. Since my last post showing different heatmap- and piece statistics got removed for not being specific enough, I analyzed several thousand games this time trying to show the differences between different levels of player strength.
I divided the data (2017-1 of the lichess.org database) into three different groups:
1) White players below 1300 rating on lichess
2) White players between 1400 and 1700 rating
3) White players above 1800 rating
For each group I extracted 25.000 games played with the following criteria:
Rating for white according to the group
Rating difference to black at max +-200 rating
Total number of moves per side between 25 and 40 to get games that reached a similiar game state
Any time limit
The resulting average number of moves per game I got for each group were the following:
1) 32,00
2) 32,65
3) 33,19
The average game length varies a bit but the difference is below 5% so this shouldn't skew the results much.
Then I tracked how often the white side moved to which square and calculated the move-to percentage for each square (moved-to-square/total moves). Lastly I compared two groups at a time in how these target square percentages differ. A green square marks a square that was more often moved to by the reference group, e.g. a green 100% shows the reference group moved twice as often to that square in relative terms than the other group. Vice versa for the red squares. See the results in the linked album.
I also ran a test to compare two samples of the same group to verify whether the differences between the groups were real or just coincidence. Here is a difference map for two datasets with 25.000 games each for the >1800 group: Link
The differences inside the same group are much smaller and I think it shows that there are real differences in how players with different strength move their pieces.
If you are interested in more general statistics, you can check out this post.