Thanks again for the great feedback and thoughts, everyone. I am always humbled by how much discussion my countdowns generate.
There have been a few queries about Glenn McGrath's adjusted average which I want to address, because I was also somewhat taken aback with his adjusted average.
Here is a decade breakdown of adjusted averages for notable bowlers:
1990s:
| Original average | Adjusted average | Opposition average |
|---|
| M Muralitharan | 27.05 | 26.86 | 31.89 |
| GD McGrath | 22.42 | 23.77 | 30.30 |
| CEL Ambrose | 20.14 | 20.19 | 32.26 |
| SK Warne | 25.90 | 26.43 | 31.03 |
| AA Donald | 21.66 | 22.17 | 31.30 |
| Waqar Younis | 21.71 | 22.77 | 31.22 |
| Wasim Akram | 21.45 | 22.17 | 31.61 |
Of the major bowlers from 1990s, McGrath gets the largest increase in average. This is probably due to him playing many matches against the weak batting lineups of England and the West Indies and not having to bowl against his own team. Ambrose's adjusted average is almost identical to his original average due to the fact that he played 4 series against Australia in that decade, who were by far the strongest batting lineup. Muralitharan's average being adjusted down is mainly due to being in a relatively weak bowling attack who conceded more runs per wicket compared to the likes of Australia, West Indies, and Pakistan.
2000s
| Original average | Adjusted average | Opposition average |
|---|
| M Muralitharan | 20.88 | 20.38 | 32.65 |
| DW Steyn | 23.71 | 22.15 | 34.54 |
| GD McGrath | 20.97 | 20.56 | 32.42 |
| SK Warne | 25.17 | 23.89 | 33.68 |
This chart explains quite neatly how quality of opposition has a big effect on adjusted averages. Dale Steyn played against the toughest opposition batting lineups and his average is adjusted down by 1.6. McGrath's average on the other hand only has a small decrease, reflecting that even though the pitches were tougher, he still didn't need to bowl to his own teammates.
What is the most interesting is the quite sizable difference in opposition average between McGrath and Warne, even though they were teammates.
2000s matches by opponent
| Opposition | McGrath | Warne |
|---|
| Bangladesh | 2 | 2 |
| England | 17 | 18 |
| India | 7 | 6 |
| New Zealand | 11 | 11 |
| Pakistan | 6 | 6 |
| South Africa | 9 | 12 |
| Sri Lanka | 2 | 5 |
| West Indies | 10 | 3 |
| Zimbabwe | 0 | 0 |
Here we have the answer: Warne played more matches against the toughest batting lineup besides Australia, and McGrath played a lot more matches against one of the weakest lineups.
* The RPW for each opposition for each series is calculated by their RPW record the the 5 years leading up to and include the year in which the series takes place, with more weight given to more recent years. The match RPW (with more weight given to the innings in which a bowling performance occurs) is then added to the opposition RPW (at a ratio of 4:1 in favor of opposition RPW) to produce the final figure which is then divided by 32 (the historical RPW since 1877). This produces the adjustment for each bowling performance in terms of runs conceded.