The idea of the pressure index

After the par score in ODI cricket, our expert shares his insight about another concept: the pressure index.

Last time we talked of the par score in ODI cricket: it is the score that a team chasing must make to tie the match based on the Duckworth-Lewis method.

A typical ODI match has ups and downs: sometimes you think India is winning and at other times you think that Sri Lanka is more likely to win.

This feeling about which side is winning is based on our general appreciation of an ODI game. If India is chasing a huge target and loses quick wickets you feel India is losing. If India is chasing a modest target and Sehwag and Gambhir are on the rampage, you feel India is winning.

Can we quantify this feeling? Can we come up with a number that measures the probability that the team chasing will win the match?

Some years ago, I collaborated with two professors: MJ Manohar Rao – now, alas, no more – and Rajeeva L Karandikar to define the pressure index ‘experienced’ by a team chasing a target in an ODI match. This index would range from 0 (if the side chasing wins) to 200 (if the side chasing loses). If the match was evenly placed, the chasing team’s pressure index would be exactly 100.

If India lose their openers while chasing 350, their pressure index might be as high as 150. If Sehwag and Gambhir blaze to 100 for no loss in 12 overs while chasing 225 in 50 overs, the pressure index could be well below 50.

Our building block for the pressure index was the par score. If the team chasing was well ahead of its par score then it had a higher probability of winning – and therefore a pressure index below 100.

The key idea – although it wasn’t as simple as that – was to look at the ratio of the par score and the actual score. If this ratio was less than 1, i.e., if the par score was lower than the actual score then the team chasing felt less ‘pressure’ and had a pressure index less than 100. If there were now a flurry of boundaries, the pressure index would drop even lower; but if there were a flurry of dismissals, the pressure index could quickly become greater than 100.

That was the approximate idea: keep tracking the pressure index ball after ball! It was a great way to know at a glance which team was ahead, and by how much. The ball-by-ball pressure index could also be plotted graphically to produce a ‘pressure map’. This pressure map provides a wonderful instantaneous appraisal of how the ODI match went.

We reproduce below the pressure map of the India-Sri Lanka game in the 2007 World Cup. India lost this match and suffered a quick exit when they failed to overcome Sri Lanka’s target of 255. The map shows that India had some sort of a chance in their first 5 overs when the pressure index was just above 100. But the loss of quick wickets – Ganguly and Tendulkar in quick succession – sent India’s pressure index up to 144 at around the 12th over.




The Castrol Index provides another way to quickly discover which of the two teams is faring better at every point of time. Read Arvind’s article to know more.