As public sector unions prepare for a day of coordinated strike action in defence of pensions on June 30th Alex Snowdon looks the state of the union movement.

The historic demonstration by half a million people on 26 March, organised by the TUC, put this country’s trade unions firmly back on the political map. Co-ordinated public sector strikes on 30 June could be another step forward for the unions and the whole anti-cuts movement.

These developments come, however, in the context of long-term decline for trade unions. I’ve been looking at some evidence on the state of the unions today.

The Department for Business, Innovation and Skills has published its annual report of union membership. The figures are for 2010. What do they tell us?

Overall patterns

Trade union density stands at 26.6% of UK employees. This represents a fall of 0.8% on 2009. Overall, 6.5 million people are in unions, a fall of 179,000 on the previous year.

General patterns include the fact that full time employees are more likely to be in unions than part time employees, and those in permanent posts are more likely to be unionised than temporary workers. Indeed the rise in temporary employment appears to be one factor influencing the slow decline in union numbers. Also, the very low paid are not well unionised: there is 13.6% union density among those earning less than £250 a week.

The average pay of union members is £14 an hour, 16.7% higher than non-union members ( £12 an hour). But the gap between trade unionists and the non-unionised is wider in the public sector (21.1%) than in the private sector (6.7%). The benefits of unions are thus rather more obvious to those in the public sector than in the private sector.

Over the last decade union density has fallen by around 3%, but the 0.8% year-on-year decline last year may indicate a quickening of the pace of decline. There have been regional variations during the last 10 years: the North East has seen a decline in union density of 7.4%, the highest of any region, influenced by the disproportionate impact of recession.

During that period the only growth sectors for union density have been ‘the professional and admin services and wholesale, retail trade and motor repair sectors’. Union density is highest in what are designated ‘professional occupations’ (43.7%) and lowest in sales occupations (12.9%).

Gender, the public/private divide and collective agreements

Union density among women is 29.4%, a fall of just 0.1% on 2009’s figures. Union density among men, however, fell by 1.4%. Only 23.8% of male employees are in unions. A significant gap between women and men has thus opened up.

The gender difference is primarily a result of the far higher union density in the public sector, where a high proportion of women workers are concentrated.

The gulf between public and private sectors is increasing. 62.4% of all trade union members today are working in the public sector, yet the majority of the workforce is in the private sector.

Fewer than half – just 46.1% – of all UK employees are in a workplace where there is any trade union presence. This is a decline of 2.8% since 2000, so for many years now over half of workers have been in workplaces with no union.

The more worrying decline since 2000 is in the proportion of workplaces with collective agreements. The decline is from 36.4% of workers in 2000 being affected by collective agreements to just over 30% in 2010. It indicates a sharp fall in union influence.

Equally important here is the contrast between public and private sectors. Only 16.8% of private sector workers are covered by collective agrements, compared with 64.5% of those in the public sector.

Growth and decline in the history of trade unions

Historically unions have grown for two reasons: miltancy and rising employment levels. In 1910, at the start of the Great Unrest (1910-14), total union membership was under 3 million. By the early 1920s, following successive waves of workers’ resistance, 8 million workers were in unions.

Unions were built in sectors which had previously been non-unionised. Groups of workers not previously known for militancy cane to the fore, as had happened in the New Unionism around 1889-90 when unions had developed rapidly, often among non-skilled and lower-paid workers, on the back of workers’ unrest.

In the 1920s and early 1930s union membership fell, due to mass unemployment combined with serious defeats for the working class like the 1926 General Strike.

There was a rising arc of membership all the way from the mid-1930s (under 5 million union members) until the late 1970s, when membership peaked at 13 million. The main factor was growth and stability of employment, first in wartime and then during the long post-war boom. Trade unions became firmly established across large industries and employment sectors, with generally stable and permanent workforces.

The period from 1980 until the mid-1990s was one of considerable decline, from 13 million to 8 million, as a result of repeated waves of unemployment, workforce restructuring and defeats for organised workers. Since then the rate of decline has been much slower.

2011 and beyond

So, to the present. The unions haven’t collapsed in the way sometimes depicted by mainstream media. The decline hasn’t been as steep in recent years as in the 1980s, but it is still a decline – and must be cause for concern for anyone committed to a strong trade union movement.

The fall in how many workers are covered by collective agreements is the most troubling development. It is one of the most important meausres of union strength. Other key indicators, like strike levels, do of course reveal long-term decline.

The gap between public and private sectors has widened, which should be a concern for anyone wanting united resistance across the working class. The low union density in the private sector can’t be ignored. Co-ordinated action by public sector workers is one thing, but involving private sector employees too is fraught with problems when so many aren’t in a union – and even fewer are covered by collective agrements or in workplaces with a decent union presence.

History teaches us the unions will only grow again if they fight. The main battles ahead are likely to be responses to the impact of austerity.

There are considerable obstacles to the kind of widespread and co-ordinated strikes socialists want to see, but only collective action will demonstrate the unions’ relevance to millions of private sector employees, the low paid and those in precarious employment.

The spirit and politics of the student protests, 26 March and the growing anti-cuts movement has to be extended to the workplaces, not just in established public sector bastions but across the working class of 2011.