Duckworth-Lewis-Stern Method Explained
The Duckworth-Lewis-Stern (DLS) method recalculates rain-affected targets in limited-overs cricket. This guide explains the logic behind DLS, how targets change, and why it replaced earlier rain rules.
Why Rain Rules Are Needed
When rain interrupts a limited-overs match, the match is often shortened and the target adjusted. Simply reducing the overs proportionally would be unfair — a team chasing 250 off 50 overs is not in the same position as a team chasing 150 off 25, because they would have had wickets in hand to accelerate in the final overs. The Duckworth-Lewis-Stern method accounts for both overs and wickets remaining.
The Two Resources: Overs and Wickets
DLS treats a cricket innings as a combination of two resources: overs remaining and wickets in hand. A team with 20 overs and 10 wickets has maximum resources. A team with 5 overs and 2 wickets has very few. The DLS tables assign a percentage value to every combination of overs and wickets — and these percentages are used to calculate revised targets fairly.
How Revised Targets Are Calculated
When rain causes overs to be lost, the umpires calculate what percentage of resources each team had available. If Team A batted with 100% of resources and scored 260, but Team B then had overs cut (losing 20% of their resources), the target is adjusted: 260 multiplied by 0.80 = 208 — the revised target. In practice, a par score system tells both teams what score is needed at each point.
History: From Average Run Rate to DLS
Before DLS, rain rules included the Average Run Rate method and the Most Productive Overs method — both widely criticised as unfair. The 1992 World Cup semi-final between England and South Africa became infamous when rain reduced South Africa's target from 22 off 13 balls to 21 off 1 ball under the old method — an effectively impossible target. Duckworth and Lewis published their method in 1997, which was universally adopted. Frank Stern updated the formula in 2014.
Criticism of DLS
DLS is not without critics. Teams batting first in a match that will likely be shortened are said to face an advantage — they can score maximally on every ball, while the defending team must set a target that the method may later adjust against them. Some statisticians argue the model is based on historical data that may not reflect the modern high-scoring T20 era, where boundary-hitting has changed run-accumulation patterns.
Frequently asked questions
What does DLS stand for?
DLS stands for Duckworth-Lewis-Stern — named after the three statisticians who developed and refined the method: Frank Duckworth, Tony Lewis, and Steven Stern.
When is DLS applied?
DLS is applied whenever rain or bad light causes a loss of overs in a limited-overs match and both sides have had a chance to bat. It may also apply when the fielding team's innings is interrupted, requiring a recalculation of what the bowling side needs to defend.
Why did DLS replace the old rain rules?
Previous methods — particularly the Most Productive Overs rule — produced unfair results in high-profile matches, most famously the 1992 World Cup semi-final. DLS's two-resource model (overs and wickets) is statistically more balanced and has been universally adopted by the ICC.