'Density bias' and a glass half empty mentality

Chris Maisano analyses the latest US trade union membership figures and provides a refreshing antidote to those who are pessimistic about the strength of organised labour because of declining membership numbers. 'Density bias' is used to describe the commonplace tendency to judge union strength by the proportion of workers who are union members. Maisiano makes a good point that 'density in itself does not translate into power if members are not actively engaged in building the capacities of their unions or the working class more broadly. What’s the point of organizing new members if unions aren’t going to effectively use the ones they’ve already got?' He goes on to argue that today's unions are still massive social organisations and mobilising only 5% of members would create an activist base numbering hundreds of thousands:
http://www.salon.com/2013/02/08/for_unions_size_isnt_everything_partner/