Duckworth-Lewis method

In the sport of cricket, the Duckworth-Lewis method (D/L method) is a way to calculate the target score for the team batting second in a one-day cricket match interrupted by weather or other circumstance. It was devised by two statisticians, Frank Duckworth and Tony Lewis and has been adopted by the International Cricket Council as the standard method of calculating target scores in shortened one-day matches. It is generally accepted to be a fair and accurate method of assessing a target score, however due to some odd results generated, critics exist of the D/L method.

Related Topics:
Sport - Cricket - One-day cricket - Statistician - Frank Duckworth - Tony Lewis - International Cricket Council

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The D/L method is relatively simple to apply, but requires a reference table and some simple mathematical calculation. As with most non-trivial statistical derivations however, D/L can produce results that are somewhat counterintuitive, and the announcement of the derived target score can provoke a good deal of second-guessing and discussion amongst the crowd at the cricket ground. This can also be seen as one of the method's successes - adding interest to a "slow" rain-affected day of play.

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The essence of the D/L method is "resources". Each team is taken to have two "resources" to use to make as many runs as possible: the number of overs they have to receive; and the number of wickets they have in hand. At any point in any innings, a team's ability to score more runs depends on the combination of these two resources. Looking at historical scores, there is a very close correspondance between the availability of these resources and a team's final score, a correspondance which the D/L method exploits.

Related Topics:
Over - Wicket - Innings

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Using a published table which gives the percentage of these combined resources remaining for any number of overs (or, more accurately, balls) left and wickets lost, the target score can be adjusted up or down to reflect the loss of resources to one or both teams when a match is shortened. This table is regularly updated, most recently in 2004, as it became clear that one-day matches were achieving significantly higher scores than in previous decades, affecting the historical relationship between resources and runs.

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Previous methods used to achieve the same task included run-rate ratios, simply selecting the score that the first team had achieved at the equivalent point in their innings, and targets derived by totalling the best scoring overs in the initial innings.

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