Duckworth-Lewis Calculation Method, 2009 Update / Duckworth and Lewis Tables updated

Frank Duckworth and Tony Lewis have updated their tables. They were last updated in 2003 when the Professional Edition of the D/L method was introduced.

They reviewed the ODI data in 2005 but there had not been a significant change in the average scores to warrant any modification to the tables at that point. Since then, however, Twenty20 matches have burgeoned and some of the skills from this shortened form of the game have made their way into 50-over ODIs. In the early part of 2009, Duckworth and Lewis began assembling the data for a thorough review of the way the one-day game is now played. In addition, many critics thought that that the D/L method ought to be different in T20s compared with ODIs. Furthermore, the playing conditions had changed: instead of the 15-over rule of fielding restrictions, Powerplays had come in, lasting 20 overs in total which could happen at different stages of a 50-over innings. It was time for the data to be analysed in order to investigate such suggestions

After the review of nearly 500 ODIs and nearly 200 T20 matches, Duckworth and Lewis have come to several conclusions.

The first conclusion is that the average 50-over ODI total has risen from 235 to 245 and that the rate of increase in extra total runs from extra overs falls away more rapidly than previously. The second, and some would say rather surprising but concomitant conclusion, is that average scores from overs available in T20I matches is consistent with the pattern in 50-over matches. In other words, there is no evidence that a different D/L method is needed between 20 and 50 over matches (or indeed in anything else in between).

A third conclusion relates to the effects of the Powerplays. In all 50-over ODI matches the first 10 overs form the first Powerplay of fielding restrictions. Their purpose, of course, is to encourage attacking play. So batsmen tend to score well in this period. But what tends to be forgotten is that the Powerplay also provides attacking fielding positions so that wickets are quite likely to be lost in this period of play. The analysis showed that the average runs scored for the combined resources of overs used and wickets lost were consistent with what the D/L method's background formula expects. As a consequence, the D/L method does not need any adjustment for the first Powerplay.

The same conclusion applied for the end of the 15th over also, which is the end of the period when the vast majority of the bowling sides take the bowling Powerplay.

The batting Powerplay is now taken at very variable points in the innings so that detailed comparative analysis is impossible, but the analysis and conclusions from the first two Powerplays gives confidence that there is unlikely to be any effect on the application of the D/L method by the third Powerplay.

With all these reassurances on the efficacy of the D/L method, as confirmed by ICC's independent scrutiniser, the ICC introduced the revised tables which are applied by computer software within the Professional Edition, from mid-September 2009, starting with the Champions Trophy in South Africa. And it received its first use in the very first match when South Africa lost to Sri Lanka by 55 runs following the early termination of the match due to rain.

The Standard Edition of the D/L method, as explained in previous Cricinfo pages, and in the ICC's regulations, is unchanged. Clubs are thus still able to apply the D/L method without the use of a computer using the Standard Edition tables.

Comments may be made to Frank Duckworth and Tony Lewis by email.

Frank Duckworth
Tony Lewis

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