Account for the collapse of private sector trade unions in industrialised economies since the 1980s. Why has the experience of public sectors been different?

In the 1980s 54.5% of employees were trade union members but by 2000 this number was below 30%. This decline in unions can be seen through a variety of measures; in 1980 64% of all workplaces recognised at least one union, this dropped to 42% by 1998; in 1984 some 70% of employees were with a workplace which conducted some form of collective bargaining, by 2004 this figure was at 39%. Many factors have been proposed for this decline of trade unions in the private sector and to a limited extent in the public sector. [...]