Wanted: AFL coach. Experience desired.

Attractive salary package and benefits on offer. Oh, and terrific job security — relatively speaking.

Job security? AFL? That can't be right, surely.

The sports industry on the whole is notoriously volatile. Players come and go. Logos and uniforms change with regularity. Clubs can even relocate to another city.

In many codes, the coach is emblematic of this fickleness. They're hired to be fired.

Carlton said it sacked Brendon Bolton because of the club's poor on-field record under his watch. ( AAP: Julian Smith )

The AFL, however, is a relative coaching safe haven.

Whereas clubs in the English Premier League have changed more than half of their permanent managers per year since 2015, the rate of head coach change in the AFL during the same period sits at just 8.8 per cent.

Our research shows that no other major professional sporting league has so little coaching churn as the AFL in the past few years.

Even with St Kilda this week becoming the third club this season to put up the "now hiring" sign, the position of AFL senior coach might just be the safest top job in world sport.

During his tenure, St Kilda's Alan Richardson failed to take the club to a finals series. ( AAP:Julian Smith )

Alan Richardson's parting with the Saints, Brendon Bolton's sacking by Carlton and Brad Scott's early exit from North Melbourne makes it the first time there have been multiple head coaching jobs up for grabs since the end of the 2016 season.

In fact, the three-year period between 2016 and 2018 was the most stable on record for coach retention.

It was 18 months between Rodney Eade being relieved of his duties on the Gold Coast to Scott leaving Arden St. That's an eternity compared to global standards.

In a historical context, the three coaches who've left in mid-2019 were perhaps fortunate to hold on for as long as they did. Bolton had the fifth-longest career of coaches who won less than 30 per cent of their games.

Scott led the Kangaroos for the second-highest number of games of any coach without making a grand final.

And Richardson has the worst winning record of anyone to have coached at least 125 games at one AFL club.

The average win-loss record for coaches finishing up at their clubs is worse than at any point across VFL/AFL history.

Losses are being tolerated by boards more than ever before.

The reasons are many and varied, but one of the biggest factors might be an under-discussed equalisation measure introduced by the league a few years ago.

The soft cap

Most casual fans would be aware of the salary cap that limits the amount of money that clubs can spend on players' salaries.

Less well-known is the restriction placed on their off-field spending.

This measure was introduced in 2015 to defuse the arms race that had caused costs to spiral, and to increase the impact of a funding boost for the league's poorest clubs.

The football department soft cap was set at $9.4 million, with clubs taxed 37.5 cents for every dollar they spent above that amount.

The tax doubled the following season before reaching a dollar-for-dollar level in 2017.

The soft cap looks to have benefited Fremantle's struggling head coach, Ross Lyon, who's contracted until 2020. ( AAP: Gary Day )

A senior coach's salary invariably takes up the biggest chunk of a club's soft cap, so sacking one can be prohibitively expensive.

The sacked coach will usually need to be paid out the remainder of their deal, and money found for their replacement.

This exercise would likely push most clubs beyond the soft cap and into the luxury tax. If a club didn't want to pay the tax, or couldn't afford to, it would need to forgo other key staff.

Since its introduction, all clubs — rich and poor — have been reluctant to exceed the off-field cap.

Clubs question the operation of the cap

The soft cap covers most football-related jobs, such as coaching, analysis, welfare, medical and recruitment.

Brad Scott (right) stepped down as North Melbourne coach after almost 10 seasons. ( AAP: Hamish Blair )

Some AFL club employees who have spoken to the ABC say that while they understand the rationale behind curbing off-field spending, they wonder whether it has stifled innovation — particularly in the areas of analytics and game research.

AFL clubs have been relatively slow to join the analytical revolution sweeping global sport, which has rejuvenated attacking play in basketball, baseball and American Football.

This stagnation can be at least partly attributed to the fact the cap has risen by just $100,000 to $9.5 million in the five seasons since its introduction.

During that period, the wage index in Australia has risen by 8 per cent, total player payments have increased 27 per cent, but there has been virtually no rise in the total salaries for football department employees.

At a time when the AFL is facing continued criticism over the look of the game, the league has overseen a real wages cut to the men and women who have a direct influence over how the sport is played.

And it's made it harder for clubs to shake up stale coaching panels.