The Duckworth-Lewis system is widely regarded as the best method yet devised for calculating what target should be set for the side batting second when a limited-overs match either starts late or is interrupted, and hence shortened, because the weather is poor. It takes its name from the two statisticians who invented it - Frank Duckworth and Tony Lewis.
Unlike simpler mathematical systems such as run-rate, which sets targets based only on the average runs per over scored by the side batting first, the Duckworth-Lewis (or D/L) system takes into account other contributory factors, such as wickets lost and number of balls remaining. The D/L method consists in practice of a set of special tables used by the scorers who undertake working-out and displaying the revised target required.