The average UK worker took 6.4 days off through sickness last year, the lowest number since 1987, a survey by the CBI suggests.
This compares with 6.7 days in 2007, the last year surveyed.
A small improvement in public-sector absence rate, which is much higher than the private-sector rate, helped to explain the drop, the CBI said.
However, the total of 180 million sick days last year cost the UK economy £16.8bn, the business group estimated.
The CBI/Pfizer Absence and Workplace Health Survey had 241 respondents from the public and private sector, which together employ almost 1.3 million people.
Respondents to the survey estimated that about 15% of the total number of sick days were not actually due to genuine illness.
The cost to the economy of so-called "sickies" was, therefore, £2.5bn, the CBI said.
In the public sector, employees took on average 8.3 days off last year, compared with their counterparts in the private sector who took just 5.8 days off.
"Although the rate of employee absence has fallen in the public sector, it is still a lot higher than in the private sector, and this issue should be addressed, especially given that the public finances are strained," said Katja Hall, director of employment policy at the CBI.
"We estimate that £5.5bn could be saved by 2015-16 if the public sector matched the private sector's absence rate."