South Korea?s union density increased to 10.3% in 2012, up from 10.1% in 2011. The union density in South Korea peaked in 1989 at 19.8% and has been in the double digits ever since, except in 2010 when the rate fell to 9.8%. Recent changes in government regulation may account for part of the growth with an increase in trade union membership accounting for the rest.
See "S. Korea?s union density increases", Global Post, October 16, 2013