We could learn from Sweden. They have similar regulations (act) to us and a body not unlike WorkSafe. The difference is the legislation mandates business to implement a systematic work (health and safety) environment management system, complete with action plans. They have many more inspectors who regularly visit the businesses to check how they are tracking against their action plans. H&S Reps also have stronger rights to help with feeding back into the management system and action plans.

To measure effectiveness you have to have something to measure. "Improvement" is far too broad - so we would need to refine it. Improving what?

Improving workplace safety culture?. No. that is way too broad and no Inspector could ever claim to have been the catalyst for that. And it takes too long to change culture.

Improving worker engagement. No. It actually takes workers to engage. And they will do, or not do that irrespective of an inspectors involvement. But lets take it a step further. Lets say an Inspector can show he improved worker engagement. Just what did this improved worker engagement achieve? If they achieve nothing, then the inspector achieved nothing.

Improved quality of PPE being issued. But was the lower quality causing any problems. And did the better quality actually achieve anything.

Improving the number of work place injuries. How is this measured. Sure cut numbers might be reduced. But the one back strain that caused three months off work slipped past.

Improved worker training? but what did this training achieve?

See where I am going with this.

Looks to me like a scheme to make things up.

So lets go back to basic principles. What is an Inspector there for? They are there to ensure a "duty holder takes responsibility for identifying and managing the risks they create or can control." That is a long way removed from "being a catalyst for improvement"

So perhaps we are aiming to measure the wrong thing.

(Thats putting aside compliance measurements)

I agree with Andrew. What are we doing focusing on measuring the effectiveness of WorkSafe Inspectors? They are there to measure the effectiveness of health and safety management in the business. But do we hold business to account re action plans based on health and safety goals? No, an astute Board of Directors might? I'll go back to my comments about the Swedish system...Businesses are mandated to have a health and safety management system complete with Action Plans. The Inspectors review the Action Plans to confirm if businesses are making changes they themselves elected to do. Counting enforcement actions is a very poor way of measuring anything let alone success!

Expectations of WSNZ Inspectorate have to be tempered by their history and their opportunity to actually make a difference, given the arrangements they have to work within.

At the time of Pike River DoL had 70-odd "warranted" Inspectors (quite a few of whom were in supervisory or project roles, and so not frontline) undertaking "responsibility" for over 400, 000 workplaces throughout NZ. DoL management continually reported to Government on quota - that they were undertaking 1000's of inspections and many hundreds of "investigations" every year. The figures were often 'made-up' in time for reporting, and that practice was encouraged by management. The more superficial their workplace interactions, the more could be completed. Inspectors were castigated if they didn't achieve their quota - which annually management tried to increase. (For mining of course, it was an even worse ratio with only two inspectors for many hundreds of 'hazardous industry' but unregulated mines and quarries - Pike River were (reluctantly) kidded by the Mines Inspector into applying the UK gassy mines standards only months before the event.) The DoL management used to have lists of "findings" such as a worker's "momentary lapse of concentration" for writing-off investigations and injuries as investigated and solved. When the WSNZ was formed, Inspectors who had performed well under the previous regime were retained, while the new supervisors coming in often had little practical knowledge or experience as Inspectors, and continued down the same path of quota gathering.
Then there was also a decision to make a clear separation between Investigators and Inspectors, with the result that many of the Investigation pool staff who were generally more experienced staff suffered burn-out and left. Previously, Inspectors had carried out both functions, with oversight from peers and supervisors to ensure that new Inspectors gained direct learnings on what serious accidents investigation processes looked like (due to the lack of staff and the huge number of "serious harm" events - only about 1 in 10 events were actually investigated, and as noted above, often without any rigor or accident causation analysis that didn't blame the unfortunate victim.)
WorkSafe at an early stage stated that they would only recruit people who had formal qualifications as a pre-requisite - and suggested that would have been the NEBOSH certificate or diploma at least. I don't know if that happened or for how long. I do know that quite a few very suitable and highly regarded Police Detectives (looking for a change of role) were unsuccessful in being considered by WSNZ. Yet it was actually ex Police Detectives as trainee and new Inspectors who "rescued" the 2008 Tamahere Coolstore fire investigation for the DoL, so that meaningful evidence was obtained and an effective process was completed - very competent investigating Inspectors who shortly afterwards moved on.
Stu's story suggests that Inspector practices are still struggling with making a real and positive difference. WSNZ Inspectorate new processes were based on a small research project in the USA that suggested many "light" visits to workplaces kept H&S front of mind for employers, and helped to keep accident rates in check - a study that was criticised at the time, and was based on USA injury statistics! NZ are still well behind international best practice in proportion of Inspectors to the overall population, and the best performing countries for overall H&S such as the Netherlands, have quite a different approach. In NZ we can't even ratify and put into force global best practice from recent decades of ILO Conventions - so as usual poor governance leads to poor outcomes in practice https://normlex.ilo.org/dyn/normlex/en/f?p=1000:11200:0::NO:11200:P11200_COUNTRY_ID:102775.