The DLS method (Duckworth-Lewis-Stern) is one of its kind and has cricket fans and lovers engrossed. It has been questioned quite a bit over its two-decade-long history, but it remains an integral part of the rules in white-ball cricket. Sometimes controversial, at times confusing, what is the DLS Method, and how does it work? Let’s take a deeper dig into it.
What is DLS Method?
The Duckworth-Lewis-Stern (DLS) method is a mathematical calculation designed to calculate the target score for the chasing team in a white-ball game (be it ODI cricket or T20s) when the game is interrupted by rain or any unforeseen circumstances, and the number of overs need to reduce. It helps in getting a statistically fair target for the chasing team and provide result even when there are interruptions during a cricket match.
Who invented it?
Initially, it was known as the Duckworth Lewis method for several years. The DL method was invented by two England statisticians – Frank Duckworth and Tony Lewis. Hence, the name comes from the two original devisors. The two English statisticians composed the formula, and it has been in existence for more than 22 years now. Moreover, just before the 2015 ICC Men’s Cricket World Cup, Professor Steven Stern updated the formula, and his name was attached to the method, and Duckworth-Lewis (D/L) method became the Duckworth Lewis Stern method. This is how the method came to be known as the DLS method.
The Duckworth Lewis method came into existence in 1997, and it made its debut in an ODI between England and Zimbabwe (second ODI of the three-match series). It was officially accepted by the International Cricket Council (ICC) in 1999 and was also used in the 1999 Cricket World Cup, played in England. The updated DLS came into prominence just ahead of the 2015 Cricket World Cup.
Before the D/L method, Average Run Rate (ARR) was used to re-calibrate the runs needed in the second innings. It just took into account the run-rate of the team batting first, and the chasing team needed to match that run-rate in their run-chase. The number of wickets remaining wasn’t taken into consideration.
Australia had also introduced Most Productive Overs (MPO) method for the 1992 Cricket World Cup. In this, the second innings adjusted target (in case of a reduced game) was calculated based on the least productive overs of the team batting first, i.e. the target for the chasing team would be the original score minus the sum of the number of runs scored in the least productive overs by the team batting first. However, the method wasn’t determined to be foolproof.
Why and when did DLS come into existence?
Unlike sports like rugby or football, where rain doesn’t stop the game or affect it in any way, cricket cannot continue even with a drizzle. Also, cricket is a lengthier game, and the delays are longer if the rain persists. A limited overs match needs to be completed on the same day ideally. A more logical reason could be having a reserve day for every game, but logistically, it isn’t practical to have a reserve day for every single limited-overs (white-ball) game.
The prior methods seemed inconclusive and had various flaws as well. It was famously brought to light in the 1992 Cricket World Cup semi-final between England and New Zealand. South Africa required 22 runs off 13 balls when the weather played spoilsport, and rain stopped play for only 12 minutes. Two overs were lost and reduced, and the MPO method directly reduced the target from 23 off 12 to 22 off 1.
Hence, there was the need to develop some formulation to re-calibrate the number of runs required for the chasing team according to the number of overs remaining.
How does the DLS Method work?
None of the previous methods, be it ARR or MPO took into account the game’s situation or the number of wickets remaining/lost. Thus, the DLS method takes into consideration a lot of factors. These are the original score batting first, the number of overs they batted, the number of overs reduced, the number of overs and wickets remaining for the chasing team if their innings has started.
The DLS method checks the number of resources available (the ones mentioned above), like the number of overs remaining and the wickets left to calculate the revised target. Moreover, the DLS method also considers the scoring patterns (for international cricket, separately for men’s and women’s and ODIs and T20Is) and trends going around of a four-year sliding window. Hence, the DLS scores keep getting updated every year. This formula (for international cricket) which also takes into account the scoring trends, isn’t publicly available.
If the scoring trends are not considered, the formula could be simply put as follows (Team 1 is the team that batted first and Team 2 is the chasing team):
Team 2’s innings par score = Team 1’s score * (Team 2’s resources/Team 1’s resources)
The resources of the two teams are the remaining number of overs and the number of wickets left. According to these two factors, the DLS method calculates the target scores.
Hence, the teams usually have a sheet that contains DLS par scores for the team batting second in the case where rain is going to be a major threat. This sheet will contain the score that the chasing team needs to be at the end of every over or even every ball. It also has the par scores according to the number of wickets lost.
In addition to this, the DLS also re-calibrates the score of a team batting first if they have batted a greater number of overs and the game is then reduced to a specific number of overs. Basically, it is considering the fact that the team batting first would’ve batted differently (more aggressively) if they would’ve known about the reduction in the number of overs beforehand. Hence, the re-calculation of the target also takes this into consideration.
Criticism of the DLS method
There has been criticism that the DLS system gives a lot of value to the number of wickets lost. One wicket could see a massive hike in the number of runs required or even the par score a team needs to be at the end of a particular over.
The other criticism of the DLS method is that it is designed for ODIs and does not work for T20s. Currently, the same method is used in T20 cricket. it is sometimes felt that the results have been slightly unfair. But the mathematical formulation designed is such that DLS currently is the most foolproof method used in limited overs cricket.
Another popular method that is used in Indian domestic cricket is VJD method. Like DLS, the VJD method also has several calculations that decide the results of a match interrupted by weather.