- International Labour Organization:
- Industrial Relations Data (IRData) - "...includes data on trade union density and collective bargaining coverage." Accessible through ILOSTAT.
- "The UNIONS database contains statistics on trade union membership for 63 countries. These statistics are taken from official national statistical publications."
- ILO Bureau of Statistics: Statistics of Trade Union Membership (2010, unpublished)
"Data for 49 countries taken mainly from national statistical publications" - includes contact information for sources