# What is the Duckworth-Lewis-Stern method?

Formerly known as the Duckworth-Lewis method, the Duckworth-Lewis-Stern method is calculation algorithm used to fairly compute the revised target in any limited-over cricket match in which overs are lost due to rain, bad light, etc.. The original method was devised by English statisticians Frank Duckworth and the late Tony Lewis, who died in March, 2020, but was subsequently revised to better handle higher run totals by Steve Stern, who is, nowadays, Professor of Data Science at Bond Business School in Queensland, Australia and, in his own words, ‘official custodian’ of the Duckworth-Lewis-Stern method. Stern was, however, keen to point out that his revision was ‘simply an adjustment and enhancement’ of the existing method.

Prior to January 1, 1997, when the Duckworth-Lewis method was used for the first time in a One Day International (ODI) match between Zimbabwe and England at Harare Sports Club, revised targets were calculated in direct proportion to the number of overs available, based on average run rate. This older, simpler method typically favoured chasing teams, but not so in the case of the semi-final of the Benson & Hedges World Cup between England and South Africa at the Sydney Cricket Ground in March, 1992. South Africa bowled only 45 overs, rather than 50, in the time allotted but, chasing 252/6, they were 231/6 off 42.5 overs when rain stopped play. When play resumed, the over limit was reduced by two, but the target reduced by just one, so that instead of needing 22 runs off 13 balls, South Afrrica now needed an impossible 22 runs off one ball.

To avoid such farcical circumstances, the Duckworth-Lewis-Stern method takes into account the remaining resources at the disposal of each team – in other words, wickets in hand and overs in hand – at the stage of the match when interruptions occur. Obviously, as wickets fall and overs are completed, remaining resources fall, but all possible values can be pre-calculated and tabulated, while various calculators, official and unofficial, are also available.