Trade Union Membership: 2009
http://stats.bis.gov.uk/UKSA/tu/TUM2009.pdf
Annual estimates of trade union membership in Great Britain including the proportion of people in employment who are union members, and the number of employees whose pay and working conditions are affected by collective agreements. Reports that the proportion of union member employees was unchanged at 27.4% in 2009. From the Department for Business, Innovation, and Skills.