Net Run Rate (NRR) is used in the round robin stage of multi-lateral ODI and T20 tournaments such as World Cup, IPL, Champions trophy etc. ‘Ball Difference’, based on the quantum of win, is a much simpler alternative to NRR.
Ball Difference(BD) stands for the number of balls saved by the winning team. This is a familiar concept that gets included in the summary of a match when a team batting second wins, e.g. ‘Team B won by x wickets (with BD balls remaining)’. We can determine BD for a team winning after batting first by calculating the number of balls between the precise delivery when the winning run was scored until the end of that innings.
We can compare BD with NRR using the gripping contests involving England during group stages of ICC CWC 2011 .
In the opening match, England successfully chased 292 posted by Netherlands with 8 balls remaining which resulted in +0.242 as NRR at that stage. This was followed by a high scoring tie when both India and England made 338. Despite a tie, Net Run Rate changed to +0.126, but BD would have remained unchanged (8+0). In the third match, Ireland beat England with 5 balls remaining chasing 327 in another high scoring thriller. BD for England at this stage would have been +3 (8+0-5) while NRR reduced to +0.035. England defended a low score of 171 against South Africa in the next match and won by 6 runs. England was 167/9 after 45.1 overs and was bowled out 3 balls later earning +3BD for game 4. NRR at this stage was +0.054 and BD increased to +6. Bangladesh successfully chased 225 in the fifth match with 6 balls remaining to bring England’s BD down to exactly ZERO. The NRR after game 5 was +0.013. In the final match, England beat WI by 18 runs, to finish with a BD of +16 and NRR of +.072. The final points table for all teams listing both NRR and BD can be viewed here.
It can be deduced from the table that NRR and BD return similar not identical results. BD integers are simpler to understand compared to fluctuating 3 decimal points in NRR. NRR is derived from the final score while BD uses actual match data. This means that NRR will be high for a team scoring slowly in the beginning but rapidly at the end for a big win but BD will be relatively lower rewarding decent bowling effort by the losing team in the initial overs. NZ scored 114 runs in the last 6 overs to post 302 against Pak and beat them by 110 runs. Since NZ was 195/5 after 44.4 overs, the BD for this match is only 32 despite a big win. It should be noted that NRR, based on final scores only, is similarly low when a team batting second wins after a slow start suitably rewarding the losing side.
A list of all the posts on this blog about BD is listed below:
1. Ball Difference : Initial post to explore the idea.
2. Computations for Ball Difference : All the rules are described with examples for various scenarios such as Rain Interruptions.
3. Largest Margins of Victory in CWC11 : All league matches in Cricket World Cup 2011 listed by quantum of victory.
4. CWC11 points table – NRR and BD : Alternate points table for Cricket World Cup 2011 listing both Net Run Rate and Ball Difference.
5. IPL 2012 points table – NRR, BD and Margin of Victory : Two tables for IPL 2012 similar to item 3 and 4 above.
6. IPL 2012 – At a glance : A single colour coded table that combines Results, Fixtures, Points and BD with a link to every match
In February 2012, Anantha Narayanan, in his ESPNcricinfo statistics blog about ‘ODIs: a blue-print for the future‘ included this post as suggestion #7 on match level changes under the heading ‘Tie resolution in leagues‘.
UPDATE 1: A youtube channel, featuring visual representation of Relative Value Model built on the foundation Ball Difference, started in November 2014.