The DLS Method
The most famous—and most misunderstood—rule in world sport. The Duckworth-Lewis-Stern (DLS) method is the mathematical formula used to calculate targets in rain-affected limited-overs matches. We strip away the complex calculus to explain how it actually works.
Why Do We Need DLS?
In traditional cricket, if rain stopped play, matches were often decided by 'Average Run Rate' or 'Most Productive Overs'. These systems were fundamentally unfair because they didn't account for the value of wickets in hand. DLS was invented to provide a fair way of resetting a match by treating overs and wickets as 'resources'.
The Two Resources
DLS views each team as having two 'resources' to score runs: the overs they have left to face and the wickets they have remaining.
Resource Percentage
A team starting a 50-over match has 100% of its resources. As overs are bowled or wickets fall, that percentage drops.
The Par Score
The 'Par Score' is the total the chasing team needs to be at to be 'level' with the first team at any given moment in the match.
How It Works in Practice
When play is interrupted, the DLS calculation compares the resources available to the two teams. If the chasing team has their overs reduced, their target is adjusted downwards. If the first team's innings was cut short, the chasing team's target is often adjusted upwards because they knew from the start how many overs they had, whereas the first team did not.
The 'Par Score' Table (Simplified)
During a rain delay, you will often see a table on the TV screen showing how many runs are needed for different numbers of wickets lost. Here is why the target increases as you lose wickets:
| Wickets Lost | Resource Remaining | Impact on Target |
|---|---|---|
| 0 Wickets | High | Lower target (more chance to score) |
| 2 Wickets | Medium | Target stays stable |
| 5 Wickets | Low | Target increases (fewer 'batsmen' to score) |
| 9 Wickets | Critical | Target jumps significantly |
The 'Gully' Myth
Fans often think DLS is just a computer 'guessing' a score. In reality, it is based on a massive database of thousands of real matches, calculating the statistical probability of scoring from any given combination of overs and wickets.
Who Are Duckworth, Lewis, and Stern?
The method is named after the three mathematicians who developed and refined it:
- Frank Duckworth & Tony Lewis: The original British statisticians who created the 'D/L' method in the 1990s.
- Steve Stern: The Australian mathematician who updated the formula in 2014 to better account for the modern, high-scoring nature of T20 cricket (becoming 'DLS').