BEIJING -- Nearly one out of every five Chinese is now a member of a trade union, with total union members reaching 280 million at the end of June, according to data from the All-China Federation of Trade Unions (ACFTU) released Friday.

Among the members of the ACFTU, the largest trade union in the world, a total of 109 million are migrant workers who come from rural areas and seek jobs in cities.

By the end of 2012, trade unions served workers at 2.87 million small and micro enterprises, while workers at Global 500 enterprises based in China were members of 3,053 trade unions, according to the ACFTU.

From 2008 to 2013, the number of ACFTU members increased by an average of 14 million every year, it said.

The data were released ahead of the 16th national congress of the ACFTU, which is scheduled from October 18 to 22 in Beijing. Nearly 2,000 representatives are expected to discuss how to reinforce the role of trade unions in China.