Figures combined for the first time show that many more people were killed than the public previously thought.
Documents also reveal the most dangerous industry is not among those WorkSafe has been mostly focused on.
It has been a horror start to 2020 with seven on-the-job deaths so far.
That's well above the 2019 rate, which was itself 40 percent up on 2018.
In addition, all the headline figures are now higher than they were, after a landmark move to combine the fatalities notified to WorkSafe, including ACC records from the police, boating and aviation industries.
WorkSafe has just introduced this new approach, though it has collected ACC records for years - and indicates the combined figure is now more accurate.
"Last year, a decision was made to aggregate WorkSafe's own fatality count with data gathered by other agencies," it said in a statement.
"This is because the development of WorkSafe's Data Centre made it possible to share data in a more accessible way.
"Both partner agencies and WorkSafe agree that combining the data presents a fuller, more transparent, picture of fatalities in workplaces."
The combined fatality figure of 413, for the six years from 2013 to 2018, is up 40 percent on the 291 deaths WorkSafe was notified of, and told to the public previously.
In 2018 alone, there were 64 deaths, combined, not the 42 widely reported a year ago.
The combined figure is revealing key angles that were obscured before, crucially, that the most dangerous industry is the one categorised as 'transport, postal and warehousing', with 112 deaths since 2012.
This is more than any of the three industries WorkSafe has historically targeted - agriculture (109 deaths 2012-2019), construction (71), or forestry (48). A separate category of support services for those three industries also scores high, with 61 deaths.
WorkSafe admits these combined revelations might change what it targets.
It is still analysing last year's data, and would not be interviewed on this story until next week.
Work-related fatalities include both workers themselves and members of the public who die as a result of someone else's work, called bystanders. This might include a holidaying motorist killed in a truck crash.
However, the ACC figures still do not capture bystander deaths, which illustrates the many gaps that remain.
So too does the research being done and nearly complete by Otago University's Dr Rebbecca Lilley. The research uses historical datasets going back years to gauge the true toll of fatalities across all industries.
"We've been able to see there's some quite significant blind spots within that [WorkSafe] dataset, particularly around fatalities that happen on the road," Dr Lilley said.
"Inadequate data has repeatedly been highlighted as a serious impediment to reducing workplace injury in New Zealand.
"Certainly when we compare the figures we have obtained from a historical, comprehensive dataset against WorkSafe's own figures, we can see that there's a significant undercount, which points to some really big opportunities to address the significant and substantial burden of work-related fatal injuries."
Her research underscores that road crashes are by far the single largest cause of work-related deaths, a factor noted by the government's newRoad to Zero strategy.
Once the many off-road accidents are included with on-road ones, then vehicle incidents become by far the most common type of fatal accident across all sectors.
If commuters were also included, numbers would rise further, but WorkSafe was constrained by resources and what the law directed it to count, Dr Lilley said.
But if it and other agencies, including police, studied coroners' reports, as happens in Australia, then key work practices that add to deaths might be exposed and changed, she said.
"Very rarely do investigations look beyond the driver, the road conditions and the vehicle conditions.
"So there's definitely a blind spot around organisational aspects such as risk management or safety culture ... or fatigue impairing performance, [these] often are not investigated in any great depth."
The Road to Zero strategy points to industry concern that tight margins in the freight sector are causing drivers to make unsafe choices.
First Union transport spokesperson Jared Abbott said WorkSafe's new approach in presenting combined fatality figures would be useful if it shed light on truck crash deaths. Not counting these better was wrong, he said.
"I think it is wilful blindness," he said.
"I mean, if you started recording truck-related fatalities, there's no doubt that working in transport would be the most dangerous job in New Zealand."
Road to Zero strategy emphasises the road as a workplace, signalling that there is a lot more work ahead for WorkSafe and the Transport Agency.
"Stakeholders have also noted that factors such as long working hours can also impact on the safety of workers travelling to and from their workplace," the Road to Zero report said.
"It is an important part of WorkSafe's developing focus on working in and around vehicles."
The evidence is mounting about what to target: Dr Lilley's research shows four-fifths of trucking fatalities occur in the Transport, Postal and Warehousing sector.
It is also showing up who to target: Men who drive trucks are eight times more likely to die than women who do.
The research, that was currently being peer-reviewed, was the "gold standard", so it was now up to agencies to use it, Dr Lilley said.
"We certainly have been working with WorkSafe in a number of areas where they know that they have some big gaps."
WorkSafe's new fatality summary for last year is incomplete, but deaths were running at a high seven-a-month up until the Whakaari / White Island eruption.
This year, vehicle causes dominate in the seven deaths so far - four on farms, one in forestry, one in manufacturing and one in tourism.