Smith, Kohli, Williamson, Root.
All fantastic cricketers.
I had a bit of spare time on my hands today, so I thought I might look a little closer at how they measure up against each other. I know not everything is seen in numbers (and we can discuss variables), but I thought it might help to gauge how they rank comparatively and what sort of gap exists between them (if any)
Being upfront, my initial thought is that there wasn't really a Big 4 anymore as much as there was a Big 3 (with a clear #1). Root's star has been on the wane for some time now.
I thought I'd compare seasons over the last four calendar years (with Smith's gap year to be considered an anomaly to be taken into account).
Test
Kohli- (currently ranked #2)
2016- 75.93 (12 matches)
2017- 75.64 (10 matches)
2018- 55.08 (13 matches)
2019- 31.80 (3 matches)
Overall 62.58
Smith- (currently ranked #1)
2016- 71.93 (11 matches)
2017- 76.96 (11 matches)
2018- 32.14 (4 matches)
2019- 110.57 (4 matches)
Overall- 73.54
Williamson- (currently ranked #3)
2016- 47.06 (10 matches)
2017- 62.88 (7 matches)
2018- 59.18 (7 matches)
2019- 74.5 (4 matches)
Overall- 56.70
Root- (currently ranked #6)
2016- 49.23 (17 matches)
2017- 50.84 (11 matches)
2018- 41.21 (13 matches)
2019- 29.72 (9 matches)
Overall- 43.62
Based on that, there's some clear distinction between all 4 of them really. It's hard to group them together.
1- Smith
2- Kohli
3- Williamson
4- Root
Looking at ODI cricket for good measure.
Root- (currently ranked #8)
2016- 61.23 (15 matches)
2017- 70.21 (19 matches)
2018- 59.12 (24 matches)
2019- 50.55 (22 matches)
Overall- 59.59
Williamson- (currently ranked #6)
2016- 41.11 (18 matches)
2017- 42.57 (14 matches)
2018- 46.80 (11 matches)
2019- 59.25 (20 matches)
Overall- 47.56
Smith- (currently ranked #28)
2016- 50.17 (26 matches)
2017- 44.90 (13 matches)
2018- 20.40 (5 matches)
2019- 37.90 (10 matches)
Overall- 43.41
Kohli- (currently ranked #1)
2016- 92.37 (10 matches)
2017- 76.84 (26 matches)
2018- 133.55 (14 matches)
2019- 64.3 (23 matches)
Overall- 83.73
Based on that-
1- Kohli
2- Root
3- Williamson
4- Smith