Last week's piece on DRS threw up some interesting findings on how teams and players use reviews in Test cricket. This week we look at the data to see how umpires fare under the scrutiny of reviews.

A word of caution at the outset: the following analysis is far from being the final word on how good or bad any umpire is. The data analysed here is only a subset of all dismissals adjudicated by the umpires. This analysis doesn't look at decisions that have not been officially reviewed on the field. And for that reason, the figures on the actual accuracy of umpires' decisions will be different from those presented here.

To illustrate this, say an umpire has handed out 20 decisions on the field. Ten of those 20 decisions are not reviewed and say all ten of these decisions were correct, it means that the umpire's accuracy in ruling these decisions is 100%. Out of the other ten that were reviewed, let's assume eight were overturned and only two went with the umpire. Now, according to the DRS data available, the umpire's accuracy from these reviewed decisions is just 20%. However, the truth lies somewhere in the middle since the umpire has actually ruled correctly on 12 out of the 20 occasions, with an accuracy of 60%. Realistically though, there is unlikely to be such a big difference in accuracy between decisions that are reviewed and those that aren't. Those numbers are more likely to be closer to each other than otherwise. That said the following numbers are strictly an account of how umpires have fared when their decisions have been reviewed in the period under consideration.

In the two-and-a-half year period since September 28, 2017, 18 umpires have officiated on the field in Test cricket. However, only 14 of them have stood in ten or more Test matches. These include the 12 umpires on the current Elite panel of the ICC, Ian Gould, who retired after the 2019 ODI World Cup, and S Ravi. The following results are presented from the data on reviews of decisions made by these 14 umpires.

Joel Wilson and Ravi are the most frequently reviewed umpires, in terms of average reviews taken against their decisions per Test. Wilson is reviewed an average of 6.6 times per match. Ravi 6.2 times.

Of course, a more accurate indicator would have been to take reviews as a factor of the total number of decisions an umpire has taken, but we have to settle for the average-review-per-match figure because of lack of data on which umpire took what decision in a match.

Michael Gough and Rod Tucker are the least reviewed at 4.1 and 3.8 reviews per Test respectively.

Michael Gough has the highest percentage of upheld decisions in Test cricket since 28-Sep-2017 ESPNcricinfo Ltd

Arguably, Gough hasn't been reviewed as often as some others perhaps because he has been fairly good with his decisions. One of the two newest entrant entrants into ICC's Elite panel of umpires, Gough has had only two of his 41 on-field rulings overturned in the period under consideration, so, at 95.1%, he has the highest percentage of "not-overturned" decisions when reviewed. Among those who have had at least ten of their decisions reviewed, Kumar Dharmasena stands next at 78.7% not overturned, followed by Gould with 77.2%.

The other new entrant into the Elite panel hasn't had such a good time officiating on the field and is almost at the other end of the spectrum. Wilson has had 93 of his on-field rulings reviewed and has managed to stick to his decisions post review only in 64.5% of those instances. Only Nigel Llong, who had a tough outing in the recent Rawalpindi Test between Pakistan and Bangladesh, has done worse. Llong has had DRS technology back his decisions in only 63.75% of his reviewed decisions. The bottom three is completed by his Rawalpindi partner, Chris Gaffaney, who, at 64.6%, is marginally better than Wilson.

The DRS technology gives umpires the cushion of "umpire's call" in cases where it can't conclusively invalidate their on-field decisions. The degree of uncertainty is such decisions is to the extent that teams or batsmen are not penalised for reviewing them. If we don't count these "uncertain" decisions, we get accuracy numbers that take into account only those decisions where the umpire was correct beyond any doubt, at least according to the DRS mechanism. We will call this the adjusted accuracy. It's a more stringent yardstick to measure the umpires against.

Nigel Llong has had the highest percentage of his reviewed decisions overturned in Tests since 28-Sep-2017. ESPNcricinfo Ltd

By this account too, Gough comes out on top, and by some distance. His adjusted accuracy is 82.9%, 22 percentage points clear of the second-placed Gould, who got 59.6% of his decisions correct beyond any doubt. Marais Erasmus slots in next with 58.9%.

Gaffaney, who manages to avoid the wooden spoon as per overall accuracy, fails to do so when we ignore umpire's calls. His adjusted accuracy of 42.4% is the worst among all umpires. Umpire's calls have come to his rescue in 22 of 64 decisions (34.38%) when reviews have been struck down. Richard Illingworth, with 47.2%, and Rod Tucker, with 49.2%, complete the bottom three. Tucker, in fact, is the umpire to benefit the most from the umpire's-calls rule after Gaffaney. Almost a third of reviews (31.8%) against Tucker's decisions that are struck down are on the basis of umpire's call.

At an overall level, there isn't a big difference between how well the umpires adjudicate off pace and spin. However, they do tend to do slightly better off spin than pace. When pacers operate, umpires overall get 70.8% of their decisions validated, compared to 72.2% when spinners bowl. In terms of adjusted accuracy, the gap widens with decisions off spinners being correct 55.7% of the times as opposed to 51.8% off pacers. This is probably because umpires can see the slower pace of spinners' deliveries better.

More umpires have better accuracy off spin bowling than they have off pace, although unexpectedly, the two Asian umpires, Ravi and Kumara Dharmasena, are the anomalies. Ravi's adjusted accuracy falls by 19.4 percentage points off spin when compared with pace. Dharmasena's falls slightly by 1%. Barring Gough, who has had only 13 of decisions reviewed off spinners, all the other 11 umpires do better off spinners than pacers.

Ten out of 13 of Gough's decisions off spinners were correct beyond any doubt, which puts his adjusted accuracy off their bowling at 82.9%. This is the highest among all umpires. All the other umpires have had at least 20 decisions reviewed off spinners. Among them, Gould tops with adjusted accuracy of 59.6%. Gough has the best accuracy numbers off fast bowlers as well. Twenty-four of his 28 decisions have been correct without any umpire's call, which puts his adjusted accuracy at 85.7%. Ravi is the next best with 68%.

In this exercise, Gough and Gould come off on top on most parameters; Llong and Wilson are worse off than most. However, it should be reiterated that these numbers are just indicative of how the umpires have gone about their job of adjudicating dismissals in Test cricket in the last couple of years or so. Ruling a batsman out or not out is arguably the most important of tasks that umpires perform on the field. But it is just one of many their responsibilities that ensure action on the field adhere to the laws of the game.