Introducing Boundary Index, Rotation Rate and Difference

Clive Azavedo introduces three new metrics for evaluating teams.

There are two broad ways teams can score runs in a cricket match: boundaries and running between wickets.

To find out how teams score runs I have devised two metrics: Boundary Index & Rotation Rate. Analysing these two metrics simultaneously allows a profile to be formed on how teams score and concede runs.

Boundary Index is essentially an advanced form of boundary strike rate. Boundary Index is calculated by multiplying the number of runs scored per boundary ball—a figure which reflects the type of boundaries a team is scoring—by the percentage of boundary balls—a figure which reflects the frequency of boundaries. The higher the number the better. Since the 2015 World Cup, the average Boundary Index of the eight teams competing in the 2017 Champions Trophy has been 44.48.

For example, since the 2015 World Cup Australia, when playing against the other seven Champions Trophy teams, have scored 829 fours and 167 sixes, totalling 4,318 runs in boundaries. Dividing this total by the number of boundaries (996) shows that they have scored 4.33 runs per boundary. This figure is then multiplied by their boundary percentage, which is 10.43% to give a Boundary Index of 42.65.

Rotation Rate is a metric which measures how well a team runs between the wickets. Rotation Rate is calculated by dividing the number of non-boundary runs by the number of non-boundary balls. As with Boundary Index, the higher the number the better. Since the 2015 World Cup, the average Rotation Rate of the eight teams competing in the Champions Trophy has been 0.52. That means, on average, teams score 0.52 non-boundary runs per non-boundary ball.

For example, since the 2015 World Cup Australia, when playing against the other seven Champions Trophy teams, have scored 4,564 runs from non-boundaries. Dividing this total by the number of non-boundary balls, which is 8,555, shows that they have scored 0.53 non-boundary runs per non-boundary ball.

The chart below plots each team according to their Boundary Index and Rotation Rate since the 2015 World Cup and against other Champions Trophy teams, in relation to the averages which are marked by 0.00 on the x and y axis.

The chart shows England to be far and away the best batting team since the World Cup. Not only is their Boundary Index considerably above the rest but they also have the highest Rotation Rate. In contrast, Sri Lanka and Pakistan both have a below average Boundary Index and Rotation Rate.

These same concepts can applied to see how teams concede runs and in this case the lower the number the better.

The best bowling team since the 2015 World Cup has been Bangladesh, not only have they conceded fewer runs in boundaries, but they have also limited strike rotation. On the other hand, one of the worst bowling sides since the World Cup has been India who have the highest Boundary Index of all teams and a relatively high rotation rate. 

The Difference metric is a simple way to compare effectiveness in batting and bowling simultaneously. Difference is calculated by multiplying a team’s average runs per over by 50 and a team’s economy rate by 50 and subtracting the bowling figure from the batting figure. The table below is based on matches between CT17 teams since the 2015 World Cup.

In this instance the Difference metric shows England and South Africa to be the strongest two teams and Sri Lanka and Pakistan to be the weakest two teams.

Clive Azavedo is on Twitter @vanillawallah.

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CricViz is the official analytics supplier for the2017 ICC Champions Trophy – we will be providing on-screen analysis throughout the tournament. Download the free CricViz app for iOS and Android here for live coverage of the Champions Trophy. 

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