In cricket, the Duckworth-Lewis method (D/L method) is used to calculate the target score for the team batting in the second innings of a test match or a one-day match which has been interrupted by weather conditions or any other unavoidable circumstances. The D/L method is considered as an accurate method of calculation and is currently the official method accepted by all teams playing world-wide. The only drawback of the method is that the method fails to predict the outcome if the match had resumed at its normal pace.
Frank Duckworth and Tony Lewis, 2 Englishmen devised a theory in 1996-97. Their theory was put into action for the first time in a one-day match of England versus Zimbabwe the same year. ICC (International Cricket Council) formally accepted it as its official method in 2001. Many have tried to formulate this process by taking into account run-rate ratios, totaling the best-scoring overs of the initial innings or even target achieved by the former team at the same point of innings but all of them had their flaws and none of them seemed fair. Controversial matches remembered include the 1992 Cricket World Cup where according to the “Best-scoring overs” method, South Africa were left to score 21 runs from the last ball which was shortened from 22 runs from 13 balls, an achievable target.
The D/L method is relatively easy to apply, once a published reference table is available. After that, it is just a few simple mathematical calculations to arrive at the new target score. Each team has got a fixed number of “overs” and a fixed number of “wickets” in hand to score runs. A team’s ability to score runs depends on the availability of these two resources. A table used for reference lists out the percentage of these combined resources that remain according to the overs left and the wickets in hand. The resources percentage can be adjusted up or down depending on scarcity of any resource. Once this percentage is found, it is used to calculate the final score required by the batting team for a win.
The reference table used is reprinted with updates at regular intervals, with the latest table being printed in 2004. The reason for the table requiring updates is that one-day matches keep reaching for higher achievable scores with passing times. Thus, the relationship between runs and resources keeps on changing. As of 2004, there are 2 available versions of the D/L method, Standard Edition and Professional Edition. While the Standard Edition requires simple manual calculations the Professional version involves more complex calculations and requires a computer. Since early 2004, the Professional Edition has been used for all international matches. In a 50 over match, a team needs to face 20 overs and in a 20 over match, the team needs to face 5 overs maximum in order to become eligible for the D/L rule application.
The D/L method has been received with criticism on account of wickets being more important than overs in the method of calculation. It is observed that for teams chasing big targets and with a chance of rain, it is helpful not to lose more wickets and score at a losing run rate. It also does not take into account the field-restriction overs in a complete match.