Duckworth-Lewis-Stern (DLS) Method Explained Simply: Rain Rules in Cricket
A plain-language explanation of the Duckworth-Lewis-Stern method — how rain delays and interruptions are handled in ODI and T20 cricket, why the old average-run-rate method was replaced, what 'resources' means in DLS, famous DLS controversies (South Africa 1992, 2003 WC), and who invented the system.
The Duckworth-Lewis-Stern (DLS) method is the mathematical formula used to reset targets in limited-overs cricket (ODI and T20) when rain or bad light interrupts a match and reduces the overs available to either team. DLS replaced the older 'average run rate' method in 1997 (introduced by statisticians Frank Duckworth and Tony Lewis; updated by Steven Stern in 2014). The core problem DLS solves: if a team batting second loses overs due to rain, what is a fair revised target? The previous method (average run rate) produced obviously unfair results — leading to the most controversial moment in World Cup history.
The 1992 World Cup Rain Rule Disaster
South Africa vs England, 1992 World Cup semifinal (Sydney): South Africa needed 22 runs from 13 balls to win (perfectly achievable). Rain interrupted play. Under the old rain rule (highest-scoring overs method: remove the overs of fewest scoring for the team batting second when recalculating), South Africa's revised target became 22 from 1 ball — mathematically impossible. The crowd was stunned; South Africa were eliminated from the World Cup through a rain calculation that had nothing to do with the match. This incident directly led to the development and adoption of the DLS method — a better mathematical model that considers all resources (wickets in hand and overs remaining) simultaneously.
What 'Resources' Means in DLS
'Resources' in DLS is the combination of wickets remaining and overs available — representing what proportion of a team's 'total batting resource' remains. The DLS tables are pre-calculated: at the start of an innings (10 wickets, 50 overs), a team has 100% of resources. If 20 overs have been bowled and 5 wickets have fallen, a team has approximately 45% of resources remaining (roughly: 30 overs remain from 50 = 60% overs used, but 5 wickets used reduces total resources). When rain interrupts, DLS computes: what resources did Team 1 have for their full innings? What resources does Team 2 now have for their rain-shortened innings? The revised target is scaled proportionally. The key improvement over average run rate: DLS accounts for the fact that early overs (powerplay) and wickets in hand both contribute to scoring potential — a team with 10 overs left and 2 wickets lost has MORE resources than a team with 10 overs and 8 wickets lost.
DLS in Practice: A Simple Example
Simple DLS example: Team A (batting first, 50 overs, no interruption) scores 250. Rain interrupts between innings. Team B (chasing) is now given only 35 overs (15 overs removed). DLS calculation: Team A used 100% of their resources (no interruption). Team B now has 35 overs and 10 wickets — approximately 78.4% of their starting resources (per DLS tables). Target for Team B = Team A score × (Team B resources / Team A resources) = 250 × (78.4 / 100) = 196. Rounded: Team B needs 197 to win from 35 overs. The DLS calculation ensures: (a) Team B gets a lower target reflecting the reduced overs; (b) But the target is not simply 250 × (35/50) = 175 — because having 10 wickets in hand but fewer overs means Team B can score more aggressively per over than Team A could at a similar stage with fewer wickets. The 'resources' framework captures this non-linear relationship.
Frequently asked questions
What is the DLS method in cricket?
The Duckworth-Lewis-Stern (DLS) method is the mathematical system used to set revised targets in limited-overs cricket (ODI and T20) when rain reduces the overs available. It replaced the 'average run rate' method in 1997. DLS works by calculating 'resources' (combination of wickets in hand and overs remaining) for each team; the revised target is scaled to ensure the chasing team faces an equivalent challenge to the team that batted first. Named after Frank Duckworth, Tony Lewis (inventors), and Steven Stern (2014 update).
Why did the 1992 World Cup rain rule cause controversy?
In the 1992 World Cup semifinal (South Africa vs England, Sydney): South Africa needed 22 from 13 balls when rain halted play. The then-current rain rule (average of highest-scoring overs) calculated that South Africa's revised target was 22 from 1 ball — mathematically impossible. South Africa were eliminated from the World Cup through the rain calculation. The incident is cricket's most famous example of an unfair rain rule; it directly prompted the development and adoption of the DLS method by the ICC in 1997.
Who invented the DLS method?
Frank Duckworth and Tony Lewis — two British statisticians — invented the Duckworth-Lewis method in 1997 after identifying the mathematical flaws in the previous rain-rules system. It was adopted by the ICC as the official rain rule for international cricket in 1999. Steven Stern (Australian statistician) updated the model in 2014 (the update improved DLS's performance in high-scoring T20 matches where the original tables underperformed). The method has been called the DLS or D/L/S method since Stern's update; the ICC officially calls it the DLS method.