Don't know why they included two figures when two numbers would do (it appears the first graph in each is showing the definition of median and quartile).

If the top quartile of performers were consistently the top quartile, then the plots in Fig. 2B would be the same because their performance is persistent over two three-year periods. Same thing can be said of Fig. 2A but with the median.

The simpler and more intuitive way to show this would be a some way to display "skill performance", "chance performance", and "observed performance".

| -------------- | Skilled | Chance | Observed |

|---------------+------+-----+-------|

| Median------ | 50% | 25% | 25% |

| Top quartile | 25% | 6.25% | 7% |