Choosing what to do with a penalty can be the hardest decision to make on a rugby field. After a major infringement by the opposition, a captain has a number of options available—and in some positions, none of them are particularly appealing. If the penalty is on the touchline, then trying to slot the ball between the posts is difficult. And even if it is successful it will only earn three points. Opting for a scrum or kicking the ball into touch for a lineout gives a team the chance to run in a try worth five points (or seven if the try is converted), but the chances are slimmer. When there are seconds left on the clock, and a crucial result in the balance, the pressure on the captain to make the right call is enormous. Just ask Chris Robshaw. The English skipper's last-minute gamble on a lineout to beat Wales (rather than a tricky kick to draw with them) three weeks ago may ultimately have cost the hosts their place at the current World Cup—and his berth in the side.



But a look at the statistics of the 2015 World Cup pool stages, which ended last weekend, shows that there is a clear answer to the penalty dilemma—and that Mr Robshaw picked the wrong one. Tier 1 sides, who participate in either the Six Nations or the Rugby Championship (the annual tournaments that feature the best nations in the northern and southern hemispheres respectively) rarely concede tries when defending lineouts or scrums behind their own 22-yard line. This has been difficult to prove before because there are a scarcity of data showing where set-pieces are contested and what the outcomes are. However, the release of Opta “chalkboards”, which record the time and location of most in-game actions, has made it possible to measure during this World Cup. In the 32 pool matches in which they have taken part, Tier 1 nations have allowed their opponents to score a try from just 9.8% of lineouts and 12.5% of scrums behind the 22-metre line–even allowing for scores that came two minutes after the original set-piece. Unexpectedly, it makes little difference whether they are holding off another Tier 1 pack, or a supposedly inferior set of forwards from Tier 2. Both have similarly small chances of rumbling their way to the line, or building a platform for the more nimble backs to scythe their way through.

Against an organised defence, set-pieces, it turns out, are an inefficient way to score points. Every scrum a team is awarded in a Tier 1 side’s 22 yields an average of 0.91 points in the ensuing phases of play; for lineouts, that number is just 0.72. For this reason, a kicker needs only a 30% chance of success rate for an attempt at goal to be the better option. Data from goalkickers.co.za calculates the probability of any particular kick going through the posts, depending on distance, angle and the skill of the penalty-taker. Of 460 kicks attempted at this tournament, only five have fallen below the 30% threshold.

Thus, whether you are mighty New Zealand or plucky Namibia, against a Tier 1 side you should call for the kicking tee 99 times out of 100 when awarded a penalty in the opposition half. Such a conservative strategy would draw jeers from onlookers in the rugby world, who want to see teams gamble for tries. It would have robbed us of Japan’s glorious success against South Africa, perhaps the greatest ever upset in the game, as the Brave Blossoms turned down an easy kick to draw for an unlikely scrum, try and victory. But it would, in the long term, provide better returns in crucial matches that go to the wire.

In this World Cup, three important results featuring Tier 1 sides could have been overturned with the right kicking tactics. On the balance of probabilities, Samoa might just have been able to secure a draw with Scotland, knocking them out of the tournament. The Welsh, who have been goaded by the Australians about their dull “northern hemisphere preference” for using the boot, would most likely have beaten their tormentors if they had attempted more than three out of 10 penalties in the Wallabies’ half. (Australia called for the tee on seven out of eight opportunities, succeeded five times, and secured a much easier route to the final.)

And then, of course, there was England vs Wales. England could not have won by using the “kick everything” mantra outlined above; in fact, they elected to kick for six of seven attacking penalties, while Wales chose seven from seven, suggesting that the players appreciate the value of playing it safe in tight games. But the seventh and final English penalty, on which they chose a lineout, showed that they are not being supported with the right information. Owen Farrell, England’s designated kicker, later admitted that the decision "came down to a feeling of what's going on on the pitch", rather than data-driven strategy. In fact, Mr Farrell succeeds about half of the time from the position of that penalty. Not much, but a significantly better chance than the one-in-ten hope offered by a lineout. A draw wouldn’t have been disastrous by any means: according to RugbyVision.com, which is predicting World Cup outcomes based on statistical analysis of thousands of past matches, it would have given England a 73.4% shot at qualifying, as opposed to 96.9% with a win. As every pundit blessed with hindsight has delighted in saying since: they should have gone for the posts.