The Duckworth - Lewis (D/L) system was developed by two UK mathematicians, Frank Duckworth and Tony Lewis, to resolve the problem of adjusting second innings targets in rain-reduced limited overs matches in an equitable manner.

Previous systems in use in both international cricket and domestic competitions around the world tended to favour either the batting or the bowling team to, at times, an extreme degree. In the early 1990s, Duckworth and Lewis set out to develop a fair system to both teams in all circumstances.

They did this by collating the scores from every one day international ever played, and this data was used to develop models that used overs remaining and wickets in hand as 'resources'. The latest version of the Duckworth - Lewis system, the Professional Edition 2011 (Version 3.0), is now used in One Day International cricket. Despite its statistical complexity, the actual use of the D/L software is very easy and training is provided by NZC to umpires and scorers.

At ODI and Twenty20 internationals played in New Zealand, the D/L par score sheet is produced by the National Umpiring Manager and circulated to umpires, coaches, captains, and scorers. At domestic One Day and Twenty20 matches in New Zealand, the official scorers are the D/L Managers and produce the par score sheet that will then be distributed accordingly.