A whopping 133 staff have left the Health and Disability Commissioner's office since 2012, an average of 19 per year.
But the HDC says there have been no personal grievances lodged in that time and the figures reflect a soughtafter work force.
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The highest number of staff leaving the HDC in one year was 29 and happened in the 2016/17 financial year, according to figures released to the Herald under the Official Information Act.
At present the HDC employs 88 permanent staff, 31 per cent of whom are part-time.
HDC senior legal advisor Renay Duncalfe said the figures in the OIA included full and part-time workers. More than 80 per cent of staff are women.
At June 30 last year there were 37 in the complaints assessment team and 18 in the investigations team.
That number had ballooned from a decade ago when there were 11 in each of those teams, in 2008.
Between July 2013 and June last year, 43 people had left the complaints assessment team, an average of nine per year, and 17 from the investigations team, an average of three per year.
The complaints assessment team triage complaints and decide how they should be handled and whether they fall under the jurisdiction of the Health and Disability Commissioner's Act.
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The HDC was set up in 1994 after the Cartwright Inquiry into the Unfortunate Experiment , to promote and protect patient rights.
Last year it closed 2392 complaints, where more than half of those ended with "no further action".
Only 4 per cent of complaints, about 80 to 100, are investigated and some take years to conclude.
The Herald requested data back to 2000 including the reason for departure and job title but the HDC refused, saying it required substantial collation, that some information did not exist in hard copy and that it raised privacy concerns.
HDC associate commissioner of legal Jane King pointed to the office's annual reports as providing "general information about staff and staffing levels at HDC".
The most recent annual report has not been published yet but in last year's one it only lists the HDC's 10-strong executive leadership team.
That number has grown from six a decade ago. According to the 2008 annual report there were 52 staff in total, with every position and the names of all staff listed.
In last year's annual report staff salaries totalled $7.1 million but only figures for 14 staff - whose salary bands were over six figures and totalling more than $2.6m - were listed.
The commissioner's salary was $377,807 and two employees received settlements and benefits associated with "cessation" totalling $6231, down from $34,709 in 2017.
Other expenses totalled $2.4m and included $180,000 for staff travel and accommodation, $571,000 for communications and IT, and $607,000 for clinical and legal advice.
Health and Disability Commissioner Anthony Hill, who took over from Ron Patterson in 2010, said the staff turnover reflected the investigative qualities needed for the job.
"HDC attracts high-calibre people who are passionate about making a difference," he said.
"Many are young, talented professionals who during their time with us develop valuable investigative and analytical skills making them highly sought after by other employers, including law firms and other organisations offering competitive remuneration packages.
"It is an understandable step when they move to senior, better paid positions in other organisations, or head off on an OE, and I wish them well.
"I am always heartened by the number who return to senior roles at HDC after some years away."
Hill said there were a number of factors that contributed to staff turnover, in line with other complaints agencies.
"Complaints resolution by its nature can be challenging, involving difficult conversations about sensitive subject matters.
"We also need to compete with an increasing market demand for people with these skill sets and experience."
He said HDC had faced significant growth in the number of complaints received, up to 28 per cent during the past three years, without a baseline funding increase to reflect that.
"We've absorbed that growth and continued to improve our performance, closing more complaints year on year and I'd like to acknowledge the efforts of our staff for this work.
"They are dedicated people, committed to making things better for their fellow New Zealanders."