Johannesburg - A third of all workers in the formal, non-agricultural sector in South Africa are members of trade unions, the SA Institute of Race Relations (SAIRR) said on Monday.
"In the last 12 years, the rate of unionisation in South Africa increased by 12%, from 26% in 2000 to 29% in 2012," the SAIRR said.
By contrast, the rate of unionisation in developed countries in 2011 was 18%.
South Africa's most unionised sector in 2000 was mining and construction, at 34% of all workers in the industry.
In 2012, it was the community, social services, and utilities sector, at 47%. Public sector employees made up the bulk of this figure.
Trade union membership in the public sector grew 18% between 2000 and 2012, but decreased in the mining and construction, trade, and finance sectors.
Congress of SA Trade Union (Cosatu) affiliate membership accounted for 75% of the total number unionised.
SAIRR researcher Boitumelo Sethlatswe said rival union membership figures came from Cosatu and therefore could be underestimated.
Most of Cosatu's members, at 38%, were elementary workers or labourers. Workers in management positions made up only 2% of its membership.
"According to Statistics South Africa, unionised workers earned more per month in 2011 than workers not belonging to a union," SAIRR said.
"The median wage for unionised workers was 129% higher, at R5 500 compared with R2 400 for non-unionised workers. Some 52% of Cosatu members earned more than R5 000 a month, compared with only 22% of non-Cosatu workers."
While two thirds of workers were not unionised, a large number enjoyed the benefits of unionisation through the 48 bargaining councils in the various sectors of the economy, said Sethlatswe.