Spinners averages are influenced by time of year and innings number. I’ve had a go at quantifying these effects, and looked at the (smaller) impact on pace bowlers. Along the way I’ll make a couple of observations on fourth innings chases.
Starting with spinners, it won’t surprise you to hear that early season English conditions are unfavourable. The first innings average for spinners before August is 59. Spinners are little use in May and June, when pitches are damper and less worn. Twirlymen are generally passengers in the first innings of a match.
Spin bowlers average 15% less in August/September than May/June. While spinners are generally more effective in the fourth innings, it’s July when they are matchwinners. Averaging 22, with 49 wickets (so a decent sample size). Next consider the same view but for pace bowlers:
Much less variation with the seasons for quick bowlers; this graph is much greener, pace bowlers are always a good thing. Averages dropping about 10% from spring to summer. A pronounced dip in the fourth innings (23) against averaging 30 in the first three innings. The sweet spot data point, again, is that fourth innings in July.
Combining spinners and pace bowlers, over the last decade the fourth innings yields 19 runs per wicket in July, compared to 28 in other months. The reason is somewhat counter-intuitive – pitches start out best for batting in July. The higher averages in the first three innings at that time of year mean the fourth innings in July start on average 20 overs later than at other times of year. Cracks, footmarks, the works. Just 3 out of 21 fourth innings chases were successful in July. Conversely, batting last in May/June was successful 5 times out of 13: a 250 chase is achievable.
Here’s a handy guide for captains of when to bowl spin in England. When do spinners average less than pace? (Or “Should I bowl my spinner if I have a fresh pace bowler?”)
I’m being somewhat glib (pace is less effective with an old ball and July 31 is not magically different from August 1), but teams do get this wrong. Just because spin is most effective in the fourth innings doesn’t mean any spinner is the best option. West Indies failed to defend 191 in the fourth innings in May 2012. Marlon Samuels (off spin, part time) bowled ten overs for 51 – Fidel Edwards only got eight overs.
What about the middle overs of the fourth innings? We can have a go at “spin or pace in the fourth innings with an old ball,” by comparing outcomes for spinners to the fourth bowler used (if they are a pace bowler). On this measure spin wins with an average of 25 against 27 for the fourth bowler used. Meanwhile opening bowlers have more fun in the fourth innings in England, averaging 22.
When slow bowlers look ineffective (early in the summer and early in every match), that’s because they are ineffective. They are still helpful in the fourth innings, but don’t give them the new ball. Spinners are probably overused and overselected in Tests in England.
Keeping things topical: Yasir Shah (Test average 30) should seldom bowl overs that could be Mohammad Abbas’s (Test average 21).