Cricinfo - Blogs - It Figures - Measuring Team Stability

Even multiplying the number of matches by 11, and dividing by the number of players (13.4 for 2009, 9.9 for 2008), giving an average number of matches per player in the calendar year, is not really useful since it doesn’t allow comparison between different years when different numbers of matches were played.

In the end, I decided to start with the premise that each calendar year commences with a match in which eleven players take part, and to then measure the changes that occurred subsequent to that first match.

So, for 2009, after the first match, we had another 21 players representing Australia in the next 38 matches, giving a stability index of 0.55 extra players per match. In 2008, it was another nine players in 17 matches, for an index of 0.53.

Doing this for Australian teams in each calendar year since 1979, when ODIs became an integral part of the cricket scene, gives the following results:

Year-wise stability index for Australia since 1979
Year	Matches	Players	Stability Index
1979	13	30	1.58
1980	9	23	1.50
1981	17	24	0.81
1982	15	20	0.64
1983	23	22	0.50
1984	22	21	0.48
1985	21	24	0.65
1986	23	18	0.32
1987	24	22	0.48
1988	15	18	0.50
1989	18	21	0.59
1990	23	18	0.32
1991	14	17	0.46
1992	21	19	0.40
1993	17	20	0.56
1994	30	23	0.41
1995	13	22	0.92
1996	26	20	0.36
1997	19	26	0.83
1998	25	23	0.50
1999	37	21	0.28
2000	23	17	0.27
2001	21	19	0.40
2002	29	21	0.36
2003	35	21	0.29
2004	26	20	0.36
2005	29	23	0.43
2006	29	23	0.43
2007	34	21	0.30
2008	18	20	0.53
2009	39	32	0.55

The table indicates that the Australian team has been less stable over the past couple of years than in the previous nine years, an era of great success for the team. There are significant spikes in the years preceding World Cups (eg, 1995, 1997-98), presumably as selectors experimented with players in an effort to strike the right combination, while the World Cup years themselves seem to be more stable.

The two years just after the cessation of Kerry Packer’s World Series can be seen as being the most tumultuous in terms of team selection, with an average of over 1.5 new players per match. After that, the benefits of having a stable team became to be recognised, and the ratios dropped quickly, although not initially to the levels reached in the 2000s, Australia’s ODI golden age.

There is much more that can be investigated here, including looking at other teams, and correlating team stability with team success.

Hi Ric,

In the first place thanks for the post. Good to see a meaningful analysis. This was something I myself wanted to do... As you rightly mentioned Aussies have been quite stable over the last decade...last two years they are trying out players to figure out their new combination for future...Im sure from 2010 to 2020 the team would again regain stability....

As an addition to your post I would like to mention that in Test, from 1990 to date, England have had 103 debutants (highest among the top 8 nations) followed by WI (87) & Pak (81)...Clearly this shows the kind of instability all 3 teams are in... most stable is again Aussies (62) closely followed by SL (66), SAF (68). The teams in mid range India(72) & NZ (74)
Interesting that SL have had quite a stable side in the last 2 decades...

I like the way you account for different number of matches played in a year - your measure is simple, easy to understand, and gives sensible answers.

Where I would suggest a slight modification is that there is more to team stability than the simple number of players used. A team with 10 fixed players which makes just one change half way through the year is more stable than a team which keeps choosing a different XI from the same squad of 12 players.

However, simply counting team changes instead of new players will not do either. A team with 10 fixed players which keeps swapping the same two players over is more stable than one with 10 fixed players and a different 11th player each time. Your measure accounts for this.

A measure only slightly more complicated than yours would count 1 each time a completely new player (for that year) joined the team and 0.5 if a player returned to the team. Then divide (as with your measure) by one less than the total number of matches.

Following Pelham Barton's comment, the fact is that not all changes to a team are equal contributors to instability. So if you had the same 11 every game, but a new captain each match, that would destabilise a team much more than swapping a few fringe players in and out. Also, having a different opening combination is more destabilising than having a different no.6 or different 4th bowler. How you accommodate all these variabilities is difficult! I'd suggest incorporating into your equations a couple of extra measures, eg: no. of players who played in, say, 80% of the games (to see how big the team's core versus its periphery was - a larger core indicates a more stable team); no. of captains/vice captains used; no. of different new ball combinations, and nos. 1,2 & 3 combinations with the bat; no. of different wicketkeepers.

Ric's comment: You could do all of these things, but it is making it much more complex. My aim was to create a simple measure quantifying team changes over the course of a year. I do like your idea of looking at the core component of a team, and I am sure there would be way of using that as a basis of measuring these team changes.

Hi Ric
It is generally understood that instability in a team will lead to a team loosing more often. It would be interesting to add another column to your list for % of games won for each year. To compare this against other nations would also give an idea of depth and strength of the side.
Cheers
Ben

Ric's comment: Yes, Ben, adding that results data in gives another whole dimension to this analysis. I'll maybe have a look at doing that soon - thanks for the suggestions.