How Good is the 30 Over Rule?

There are many pieces of cricketing wisdom.

“Bring your spinners on for a grassy pitch.”

“Never bat first on a poor pitch.”

And, of course, my personal favourite:

“Double your score after 30 overs in a one-dayer.”

During the 2015 Cricket World Cup, people began to notice that this rule wasn’t all it was cracked up to be. Teams always seemed to be overshooting the rule.

And now you’ve got proof.

Teams are, in fact, going over the mark, by an average of 18%.

Not having a massive stats lab on my hands, I used the 2015 World Cup to get an estimation on the accuracy of the rule. Teams had to have batted first and had an innings last all 50 overs for inclusion in the database, and 32 different innings got in.
30-over test

The closest innings was the first one of the World Cup. New Zealand scored 331, just one less than that predicted by the theory.

25 out of the 32 innings had a team overshoot the mark, 21 of those by more than 10%. In two of the matches (South Africa-West Indies and West Indies-Ireland), the teams were closer to tripling their score than doubling it.

There’s some proof that the 30-over rule isn’t all it’s cracked up to be. However, I’ve thought of something else we can test with this:


The bigger the ratio, the more likely you are to win.

This seems to make intuitive sense. After all, if you have a higher ratio, you’ll score more runs.

Except…that’s not exactly true. The highest ratio here, West Indies v Ireland, is based off the lowest score after 30 overs.

Let’s look at the data.

  
You’re 20% more likely to win if you go over the ratio than if you don’t.

So, the final verdict: the double after 30 rule is a conservative estimate. Your team should score at least that if they’re in for a shot at winning.

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2 comments

  1. I always thought the rule of thumb was take ten times the number of wickets fallen and then double the score was the rule. In that case the estimate is even more conservative since most teams arent none down at 30 overs.

    Like

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