Short Stat: Stability and performance
Russell Degnan

We know such an approach is a good thing. There is an obvious correlation between that and success, though which is the chicken and which the egg is debatable.

- Rob Smyth - The joy of selection roulette

The need for stability is always the catch-cry of teams struggling, and players fearful of their places. It has been an article of faith that Australia built their dynasty around youth in the 1980s, though even that might need some revision.

The longest period of batting stability for Australia immediately followed the 1989 Ashes, with only the substitution of one Waugh for another in 21 tests. But it was also a period marked by weak opposition, with the only losses being in NZ and to the West Indies (2-1). The 12 tests that followed the enforced retirement of Geoff Marsh, leading up to the 1993 Ashes, was anything but stable, with 6 different openers, 4 different players at first drop and 6 more players in the middle order - 7 of you include Greg Matthews. The results? Only three losses, one in NZ, and a 2-1 loss to the West Indies. Another two top-order changes were made for the first test in 1993; as in 1989, Australia were 4-0 up by the final test.

Perhaps results might have been better with more stability (a series lost by one run has a lot of what-ifs); or perhaps the opposition over-rides whatever difference might exist. It is reasonably unlikely that swapping the 6th best player for the 7th makes a big difference, though ongoing panic such that you select the 13th best, might.

To factor out the opposition, we can compare the expected margin against the actual result, and graph that against the number of changes made. There is a lot of noise:

There is also some indication that making zero changes is better. In the short term, the best side is probably the one you thought was the best side. But making one or two changes is still likely to produce a (very slightly) above-average result - note that 20 ratings points equates to 10 around runs, a fifth that advantage conferred by playing at home. Though this doesn't necessarily solve Smyth's chicken and egg quandary, as a result above expectations may merely represent below average expectations.

It gets more interesting when we look at changes per match over the previous two years. A side in constant flux ought to under-perform relative to expectations, if stability matters.

Actually, we don't see that. There is a lot of noise, and the difference is minimal, but sides making fewer than 1 1/2 changes per match do worse than expected than those making more.

I'd proffer two possible explanations. Firstly, that there is an information problem, in finding the best set of cricketers, and most likely some benefit in trying several out until one shines sufficiently to become more permanent. And secondly, that stable sides are more likely to be older sides - established, successful - and therefore more likely to be declining in performance. That doesn't mean an alternative player will perform better though, particularly in the short term. As the game to game suggests, more often than not, the best players a team has are those who've proven to be the best they have, even when they are losing.

Idle Summers 12th June, 2014 19:35:33   [#]