Exit and Entry

Our next problem is caused by the fact that twice, test playing teams have been excluded from the sport for political reasons.  South Africa in 1970 and Zimbabwe in 2005 were both suspended.  Each subsequently have returned.

When suspension occurs, it’s easy to work out what to do. We remove the team from the ratings; and adjust the ratings of the other teams up or down as appropriate to keep the mean rating at zero.  It's more of a problem when the team returns.

There are a number of options here.  One is to return the team at the rating it had when it was expelled.  But this does not seem satisfactory. South Africa were the best team in the world when they were kicked out.  Over twenty years later, with none of the players they had in 1970 still in their team, it would be crazy to reintroduce them at the top of the rankings, just because they’d been good two decades previously.

The next option is to treat their return as if they were a new team, at the bottom.  But when South Africa first played a test match in 1888 they were a developing cricket side.  By contrast, they were still an advanced cricket-playing nation when they returned in 1992 – domestically, cricket had still been played, even though they’d been banned from international matches. It seems absurd to assume they had regressed to the level of one hundred years previously.

So perhaps we should re-enter them at zero.  But Zimbabwe had never had a rating as high as zero in their first spell in test cricket.  To set them to zero on their re-introduction would have been to assume they were returning stronger than they had ever been before. This also seems wrong.

I considered one other possibility: re-introducing a team at its average rating during its previous spell.  But ultimately, this seems a little too cute; and one could imagine in future a country leaves test cricket, its internal cricket culture completely changes (imagine a civil war, say, which leads to the complete abandonment of the sport, followed by its subsequent reintroduction), and when it eventually returns to the test arena its previous results really are no guide at all.  In the end, I decided to reintroduce teams at the bottom, just as if they were starting out. It should be noted that under this system, by 1995, South Africa’s rating reaches a positive (i.e. better than average) rating and by 1998 the team have claimed first place once again.  So although the system appears harsh, it doesn’t have the effect of permanently imparining their rating (and in fact, under the ICC’s system, it took South Africa a further year to reclaim the number one spot).

We’ve now almost finished our discussion of how my ratings are calculated.  But before we continue to look at the current ratings, we need to go back to our discussion of the k-factor.  That will be our next subject.