News

# A simple explanation of the Duckworth Lewis method

Over the course of this season there have been several Somerset matches where the Duckworth Lewis method has been called into play

Richard Walsh
22-Jul-2002
Over the course of this season there have been several Somerset matches where the Duckworth Lewis method has been called into play.
Chris Bass who operates the scoreboards at Taunton has sent the following explanation of the system in the hope that it will help website readers to understand the method a little more clearly.
'The Duckworth/Lewis method for re-setting targets in modern one-day cricket has gained an unjust reputation for one basic reason - people simply do not understand it. Anything that one does not understand tends to make people switch-off and join the ranks of the critics.
Coaches and players need a simple understanding of D/L because it does exist and affects their decision making, just as the latest 2000 Code of Laws has done.
Spectators want to know in the simplest terms what the D/L figure on the scoreboards actually means in any potential situation. This brief guide is designed to outline, explain and simplify the method as clearly as possible.
Why Duckworth Lewis?
The traditional method used up to 1997 to revise targets when weather interfered with limited-overs cricket was based on average run-rate. The only advantage of such a system was that it was easy to understand and calculate for all concerned - players, officials and spectators - but it almost always gave a hugely unfair advantage to the team batting second, with the result that captains winning the toss when rain was around almost always chose to field first.
From 1997, the ECB adopted the Duckworth/Lewis method as a fairer system, since when the ICC has done likewise. Before the days of D/L, there were some horrific examples of the average run-rate method producing ridiculous situations - today there are few. D/L is now generally accepted by players who understand it as by far the fairest method yet devised for target resetting.
To avoid the spectacle of the batsmen meeting in mid-wicket and consulting Duckworth/Lewis tables and pocket calculators between every over, the scorers and Match Manager generally do the calculations and display the difference between the runs achieved and the score needed to win - if the match were to be finished at that instant - as a figure on the scoreboard, so all can see whether the batting side are ahead of or behind the target.
Who are Frank Duckworth & Tony Lewis?
These two gentlemen are in fact professional statisticians and mathematicians who work closely with the ECB. They have done extensive research into past limited overs cricket matches, updating and improving their own system over the last 5 years.
What is the D/L Method?
In simple terms, the D/L system converts the number of overs remaining and the number of wickets lost into a "resources remaining" figure. As overs are completed or wickets fall - the "resources remaining" falls.
When a limited overs cricket match is delayed or interrupted by rain or bad light, there is often insufficient time for both teams to complete their full allocation of overs. It is therefore necessary to calculate a fair target for the team batting second - taking into account the number of overs that they will face.
D/L has far fewer anomalies than any previous method. Whenever rain interrupts a match, the D/L method is designed to leave the balance of the match unaltered.
Where other earlier methods crucially overlooked the importance of wickets lost at the point of delay, the D/L method incorporates this factor into its calculation. It is obviously much easier to chase 100 runs with ten wickets left than with just three wickets standing and the D/L method was the first of its kind to recognise this.
The D/L Method in Practice
The adjustments that the D/L method makes try to ensure that after a rain break, the status quo of the match is roughly retained. If the 'chasing' side is ahead when rain arrives, then they are awarded the match if no further play is possible. This has given rise to a whole new tactical approach for teams batting second.
Although the D/L method consistently spits out fair equations, which are easily understandable, its more intricate formulae are highly complicated and far too difficult for the ordinary man to comprehend. However, players and spectators do not need to bother themselves with more than a grasp of how the system operates and how it might affect tactics in any one-day match.
The method revises a target in the event of an innings being reduced by rain, or any other suspension of play. The revision is not worked out, or affected, by the number of overs each team SHOULD receive, but in accordance with the 'run-scoring resources' each of the sides has at its disposal.
These resources include a combination of overs left and wickets remaining. If only things were that simple, especially the weather! Either innings could be interrupted, possibly several times, or cut short. But the Duckworth/Lewis system is designed to cope with anything the weather can throw at a game.
For example, if a side is set 300 for victory - a tough target in any conditions - and rain is forecast, it is likely that they will go on the attack from the outset to try to stay 'in front' of the opposition.
A team with 6 wickets still standing with 10 overs to bat will take risks to score quick runs. Some simplistic target setting led to several infamous disasters where the required demand on the team batting second was very obviously unfair.
The D/L Method in Practice at Taunton
At the County Ground, both scoreboards display the D/L target score for the chasing team from the start of their innings. The number shown is the total required to win at each stage of the innings after the first 10 overs.Whenever a wicket falls, this total will possibly rise dramatically. Otherwise, the adjustment upwards at the end of each over is likely to be small.'