The Duckworth Lewis method or D/L method is a set of formulas and tables created by Frank Duckworth and Tony Lewis. The method was adopted by the International Cricket Council (ICC) in 1999 to address the problem of delayed one-day cricket matches for reasons of rain, poor light and floodlight failures although it has also been used in events that have been shortened due to crowd problem, sandstorms and even snowstorms.
The calculator is based on the standard edition of the calculations which are accurate for first innings scores of up to 235, the resource table used is the most up-to-date as per the 2004 revision 2 duckworth/lewis ball-by-ball table. The Professional edition of Duckworth-Lewis (aka CODA) would be used by officials for first innings scores greater than 235.
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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 correspondence between the availability of these resources and a team's final score, a correspondence which D/L exploits[3].
ReplyDeleteUsing 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 one or more times. This percentage is then used to calculate a target (sometimes called a 'par score') that is usually a fractional number of runs. If the second team passes the target then the second team is taken to have won the match; if the match ends when the second team has exactly met (but not passed) the target (rounded down to the next integer) then the match is taken to be a tie.
The D/L method has been criticized based on the fact that wickets are (necessarily) a much more heavily weighted resource than overs, leading to the observation that if teams are chasing big targets, and there is the prospect of rain, a winning strategy could be to not lose wickets and score at what would seem to be a "losing" rate (e.g. if the asking rate was 6.1, it could be enough to score at 4.75 an over for the first 20-25 overs).
ReplyDeleteAnother criticism is that the D/L method does not account for changes in the proportion of number of overs during which field restrictions are in place compared to a completed match.
More common informal criticism from cricket fans and journalists of the D/L method is that it is overly complex and can be misunderstood.