South Africa lost R3.9-billion worth of output last year to sick leave and absenteeism, recruitment company Adcorp said on Thursday.

"The cost to the economy has been enormous. Due to the unplanned and unpredictable nature of sick leave, the knock-on disruptive effects on supply chains has probably been greater than these figures suggest."

Average output per worker was R140 855 a year, or R574.92 a working day.

In 2011, 3.4-million workers were absent because of sick leave, according to the Adcorp Employment Index.

Sick leave taken had increased by 397% from 2000, when 0.7-million workers were absent.

In real terms, the economy had lost a cumulative R47.5-billion since 2000.

Between 2009 and 2011, a quarter of all workers took up in full the maximum statutory allowance for sick leave, of 36 days in a three-year cycle.

"Sickness-related absenteeism has increased four-fold since 2007," Adcorp said.

This was despite the fact that employment numbers were virtually flat over the decade.

The rise of absenteeism may also have contributed to the growing phenomenon of temporary or contingency workers, the company suggested. Roughly half of agency workers were employed as substitutes for absent employees.

Absenteeism was most pronounced in the government sector. A third of public sector workers were absent for health reasons, compared to 9.2% of private sector workers.

Poor managerial oversight, lax administrative controls, outmoded information systems and weak human resource functions in the government sector appeared to contribute to the poor control of absenteeism, Adcorp said.

Heavily unionised sectors such as mining, transport, logistics, and utilities were also affected. Non-unionised sectors such as finance, personal services, communication, wholesale and retail trade, and agriculture, were less affected.

In genuine cases of illness, the nature of the work itself could be implicated. However, in false cases, the take up of sick leave allowances could be a function of how generous those allowances were, and the degree to which absenteeism was monitored and controlled.

"It is alarming that sick leave in South Africa has been rising continuously over the past decade, with no signs of reversing," Adcorp said.