Each of the three Tests played over the last week produced outright results, and that happened despite poor weather affecting the games to varying degrees.

Two of those matches - the thriller between England and Australia at Headingley and the one in Antigua between West Indies and India - didn't need the scheduled fifth day. Funnily enough, the game that actually went into the fifth day was the shortest of the three in terms of playing time: only 275.4 overs were bowled in the Colombo Test between Sri Lanka and New Zealand, but time almost ran out for New Zealand on the last day as it looked like the light would fail. The Antigua Test was the longest of the three, but even that lasted only 310.2 overs, less than four full days of cricket.

So, even as the bosses of the game mull four-day Tests to make the longest version of the game more compact, the format itself seems to be shrinking organically.

There have been 67 five-day Tests since the beginning of 2018 and 40 of them have finished within four days, or sooner. That's a record-breaking 60% - no two successive years in Test history have had such a high proportion of matches getting over with a day or more to spare.

In 2019 alone, 13 out of 19 five-day Tests have finished within four days - that's 68.42%, the highest ever for a calendar year in which a minimum of ten Tests have been played. This is not a blip either. The last three calendar years are among the top five in Test history in terms of matches finishing a day before schedule. In 2018, 56.25% (27 of the 48 five-day Tests) of matches finished within four days. In 2017, it was 47.83%.

Since the beginning of 2018, almost two out of three matches have finished within four days. In comparison, only 47.78% (97 out of 203) of matches have finished early in the period from 2015 to 2019. In other words, the last two calendar years have seen nearly a 25% increase in early finishes. Since the turn of the millennium, 43% of matches have finished within four days.

Clearly, Test cricket has come a long way from the dour 1980s and 1990s; in the 20-year period from 1980 to 1999, only one out of 3.6 Test matches finished within four days. The last couple of years have halved that frequency.

Even of those matches that have gone into the fifth day, since the beginning of 2018, not all have actually seen more than four days' worth of overs being bowled. A third of these spilled over to the final day because they were hit by bad weather. In the last five years in Test cricket, the average overs sent down in a full day of play works out to 88. It follows that a Test may be considered to have gone beyond four days only if it lasts for more than 352 overs.

By that yardstick, only two of the 19 five-day Tests played this year have actually seen more than four days' worth of cricket - the first Ashes Test and the one in Galle this month. Two of these 19 matches - the Sydney Test involving India and the second Ashes at Lord's - ended in draws, but saw fewer than 300 overs being bowled. The Lord's Test, in fact, could have produced a result if another session of play had been possible.

Since the beginning of 2018, as many as 49 out of 67 five-day Tests have not lasted more than 352 overs. That's almost three in four matches that haven't gone into the fifth day. In comparison, the percentage of early finishes since the turn of the millennium has been just over 50%. The last couple of years have seen a 46% increase in matches that finish within four days' worth of play in comparison to the last 19 years, and a 26% increase when compared with the last five years.

Importantly, these trends are being seen almost all over the world. Australia are the only exception - arguably because of the flatness of drop-in pitches. Only two of the six matches that ended in a decisive result in Australia since 2018 have had less than five days of play. However, of the four that went into the fifth day, the Ashes Test in Sydney in January last year was the only one that wasn't played on a drop-in pitch. The day-night Test earlier this year at the Gabba - the other major venue apart from the SCG not to use a drop-in strip - ended in just three days (213.5 overs).

Apart from Australia, all other host countries have seen at least half the matches finish with under four days' worth of cricket. Since 2018, the UAE is the only place where less than two-thirds of the matches have finished within four days. Even there, three of the four matches that ended with an outright winner ended within four days' worth of bowling.

It is good news that 2018 and 2019 have seen an unprecedented share of matches yielding a decisive result. Incredibly, 18 of the 20 matches played this year and 61 of the 68 played since last year have ended with a winner. These two years rank in the top two in terms of calendar years that have seen the highest percentage of decisive results in Test history (with a minimum of ten matches played).

The higher the number of decisive results in a year, the more likely there are of early finishes. But even if we consider only the Tests that ended in a decisive result (and ignore draws), the percentage of matches that have ended before five days are more in the last couple of years than they were earlier. Since 2018, 49 out of 60 five-day matches that ended in an outright result were early finishes, which is nearly five out of six matches. That is one early finish more than what we have seen since the turn of the millennium.

Moreover, the median length of Test matches that have ended in an outright result in the last two years has been just under 1800 balls - 300 overs a match. That means half of those Tests ended in just over 11 sessions of play. The corresponding number for the period 2015-19 is 1914 balls, which means an average match with a winner and a loser since 2018 is ending 19 overs sooner than an average match in the last five years. An average Test in 20 years before the turn of the millennium (1980-1999) took nearly 30 overs more to finish than it is taking nowadays.

A sample size of only 60-odd matches makes this at best a theory that will be put to test in the next couple of years. But there are signs that do point to shrinking Test lengths. Batsmen in the T20 era are less likely to bat long: there have been only five innings of 250 balls or more in 503 innings this year by top-order batsmen. That's only one out of a hundred innings. Twenty years ago, such an innings was five times more likely (50 innings of 250+ balls out of 1030 in 1999).

These are good times to be a Test bowler too: bowling strike rates have been the lowest they have been in over 100 years.

The World Test Championship is going to add its own impetus to the push for decisive results in Test cricket in the future (dampened only by late-stage points-table dynamics). It's likely that before long, the bosses will see the benefit in four-day Tests (and shorter series) that allow them to play the required six series in a shorter time. Test cricket could well shrink to four days - both organically and inorganically.