Growth during the 1970s in the local government employees' union NALGO, for example, took place in new white-collar job territories, as no other union "was capable of recruiting these non-unionised workers." Selective recruitment in nonunionized sectors (by the TGWU and particularly ASTMS), and the spread of shop stewards ("the most effective recruiting agent") in the TGWU --and in some NUGMW and construction workers' union (UCATT) regions--almost certainly resulted in membership growth without adversely affecting other unions.
accept that growth in individual unions is not conclusive evidence of the factors affecting total union growth, but they say it does suggest that union leadership and organization are of importance, and "aggregate theories that discount internal factors may be oversimplifying the causes." Furthermore, the activities of "open" unions like ASTMS and the TGWU disturbed the inter-union status quo and stimulated competitive recruitment, as did more growth-conscious NUGMW leaders.
NUGMW: National Union of General and Municipal Workers (now GMB)