T20 Ratings - World Cup Edition
Russell Degnan

This won't be a regular thing - to the extent that the test ratings are regular. But it occurred to me that with relatively few games to consider, and most of the ratings leg work done already, converting the 300 odd T20 games to a workable ratings system was feasible.

The main difficulty was deciding on the starting ratings, given the "minnows" have no form, and moreover, were mostly playing each other prior to the start of the tournament. I settled on a modified form of the official ODI ratings at January 2005 (multiplied by 5 essentially), with the non-ranked teams set to 0, then all teams normalised to average 1000.

Weights and expected margins were adjusted to suit: the margin for a chasing team was set to:

1 + balls_remaining * (wickets_remaining / 5)

It is far too early to judge how successful that is, but perhaps by the next world cup some proper statistical analysis can be applied. The ratings prior to the start of this tournament, including all games to date (and the uncounted "warm-up" games) were as follows:

Rankings prior to World T20form
1.Australia1363.07-34.40
2.India1351.15+5.33
3.Pakistan1263.30-22.04
4.Sri Lanka1236.14-38.06
5.New Zealand1218.13+14/07
6.England1217.61+13.44
7.South Africa1192.24+20.86
8.West Indies1163.70-34.10
9.Zimbabwe982.77+46.47
10.Bangladesh934.23+34.26
11.Scotland774.35+17.66
12.Canada741.97+4.30
13.Netherlands708.84-7.58
14.Ireland707.04+22.25
15.Bermuda642.92-73.57
16.Kenya639.22-52.28

I'll keep this post updated as the tournament progresses.

Update 8th June: After six games there has been a little movement, notably Australia and Pakistan moving backwards and South Africa forwards. A little tightening has occurred in the first few days.

Update 9th June: Australia crashes out, and down, but perhaps from a ratings perspective it is better they aren't still playing as their form is at -108.9 (in comparison to South Africa's +92.6). Ireland's numbers are still low, but their form and progression to the last eight will see that improve.

Update 10th June: Perhaps unsurprisingly, Pakistan got the 25 run victory they needed - the ratings predicted 49 runs. A meaningless South Africa v New Zealand game and an error in my game details provide the other changes.

Update 11th June: Two results that went largely as expected. India and Ireland move back towards an otherwise even pack leading into the second round.

Rankings after first roundform
1.India1319.61-41.17
2.Australia1285.14-95.12
3.Sri Lanka1259.87+14.02
4.Pakistan1253.03-7.12
5.South Africa1237.09+70.62
6.England1211.91+14.83
7.New Zealand1201.58-16.44
8.West Indies1194.00+24.30
9.Zimbabwe982.77+46.47
10.Bangladesh928.76-14.36
11.Ireland772.33+78.25
12.Scotland760.12-40.65
13.Canada741.97-4.30
14.Netherlands715.01-8.60
15.Bermuda642.92-73.57
16.Kenya639.22-52.28

Idle Summers 8th June, 2009 01:01:39   [#] 

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