Union density measures the degree of penetration of either an individual trade union or the trade union movement in the workforce. The measure is expressed as the percentage of potential union members who are actually members of a union. Union density may be measured on an aggregate or a disaggregate basis: aggregate measures look at the level of union membership in the economy as a whole, while disaggregate measures look at union membership in a range of different ways. For example, analysts may wish to examine union density in different sectors of industry: public or private sector, manual workers, white-collar workers, manufacturing industry and so on; or to examine density among women workers or atypical workers . Union density overall in Ireland had been around 50 per cent. for a number of years in the 1970s and early 1980s, but by 1987 it had fallen to 43.5 per cent. There has once again been a growth in membership since then, and current union density is estimated to lie at around 50 per cent.
Density in the public sector is traditionally higher than in the private sector: The Irish Congress of Trade Unions estimates a density of as much as 90 per cent. in 1992, with only 41 per cent. in the private sector. It is important not to pay too much attention to aggregate union density figures to the neglect of disaggregate measures, since while overall union density is falling, trends among some sectors of the economy and the labour force show that union membership levels have been rising among some groups, in particular women workers and white-collar workers.
Please note: the European industrial relations glossaries were compiled between 1991 and 2003 and are not updated. For current material see the European industrial relations dictionary.