Trade unions in Colombia were, until around 1990, among the strongest in Latin America. However the 1980s expansion of paramilitarism in Colombia saw trade union leaders and members increasingly targeted for assassination. As a result, Colombia has been the most dangerous country in the world for trade unionists for several decades. Between 1986 and 2010 over 2800 labor leaders were killed according to one source, and over 4000 according to others. Most assassinations were carried out by paramilitaries or the Colombian military; some were carried out by the guerrillas. In 2009 only around 4% of workers in Colombia were unionized.