The most common cause was illness, followed by caring for a sick or injured family member or dependant, and then non-work-related injury.
About a fifth of employers also cited "seeing paid sick days as an entitlement" as a reason for absence, and suspected employees were not actually sick. But about half said genuinely sick employees would come to work more often than not.
The median cost of absences for each employee was $837, a total cost to the economy of $1.26 billion. Costs included the salary of absent workers, replacement costs, and lost service or production time.
BusinessNZ chief executive Phil O'Reilly said the costs were an indication of the "size of the prize" for businesses to manage their sick leave better.
But there was a cost to workers turning up sick, and those genuinely ill should feel supported to stay home, he said.
However, employers could work on managing leave for non-illness reasons.
"Rather than take a whole day, if the company says I'll give you an hour off to take your kid to the dentist, what you'll find is the employees will be more satisfied and happy."
Public Service Association national secretary Richard Wagstaff said public sector organisations were generally large employers, which also had higher rates of absenteeism across the board.
Public servants were also often entitled to 10 days' sick leave a year.
Staff with five days' sick leave might be taking annual leave or unpaid leave when unwell, or going to work, he said.
Mr Wagstaff said he didn't believe workers were taking unjustified "sickies" in large numbers.
Council of Trade Unions president Helen Kelly said overall, workers were taking very little sick leave. She also noted 56 per cent of employers had asked for a medical certificate after at least one day.
"It's outrageous that sick people can't just stay at home for a day in bed, that their employer sends them off to the doctor."
Numbers
• 6.1 million sick days a year, costing the economy $1.26 billion
• 6.6 days taken by public sector workers, compared with 4.3 for private sector
• 56% of employers required a medical certificate