Whether it is a sudden downpour or a floodlight failure, unpredictable interruptions are a reality in limited-overs cricket. When a match cannot be completed in its scheduled format, the game relies on a complex mathematical formula to ensure a fair result: the Duckworth-Lewis-Stern (DLS) method.
First introduced in 1997 by statisticians Frank Duckworth and Tony Lewis (originally known as the D/L method) and later updated by Steven Stern in 2014, the DLS method is the official system used by the International Cricket Council (ICC) to set revised targets for the team batting second.
The Two Core Resources
To understand DLS, you have to look past simple run rates. The method operates on the principle that a batting team has two fundamental “resources” available to them to score runs:
- Overs (Balls remaining): The number of deliveries left in the innings.
- Wickets remaining: The number of batters left to play.
At the start of a standard 50-over match, a team has 100% of its resources (50 overs and 10 wickets). As overs are bowled and wickets fall, this resource percentage drops. The DLS method uses a historical database of ODI and T20I matches to determine exactly how much run-scoring potential a team has left at any given combination of overs and wickets.
Why Was It Invented?
Before DLS, cricket used flawed systems like the Average Run Rate (ARR) or the “Most Productive Overs” method. These older systems heavily favored the team batting second and failed to account for wickets lost.
For example, under the ARR method, if the team batting first scored 250 in 50 overs (a run rate of 5.00), a rain interruption that reduced the second innings to 20 overs would simply set a target of 101 (20 x 5.00 + 1). This ignored the massive advantage the chasing team had by possessing all 10 wickets to aggressively chase those 101 runs. DLS fixed this by weighing the value of those retained wickets.
How Does It Work in Practice?
The exact mathematical algorithm is complex and kept proprietary by the ICC through computer software, but the basic application follows these scenarios:
- Interruption before the second innings: If the team batting first completes their innings but rain reduces the overs for the team chasing, the DLS sets a “par score.” Because the chasing team has fewer overs but still has all 10 wickets, their target is often adjusted slightly upward compared to a simple run-rate calculation to balance the aggression they can afford.
- Interruption during the second innings: If a match is washed out entirely while the second team is batting, the DLS software calculates the “par score” based on the exact over and the number of wickets lost at the time play stopped. If the batting team’s current score is higher than the DLS par score, they win. If it is lower, the fielding team wins.
In modern T20 and ODI cricket, teams are provided with a printed DLS sheet (or digital tracker) that shows exactly what score they need to be at by the end of each over, depending on how many wickets they have lost, allowing captains to strategize in real-time as storm clouds gather.