It's worth taking a look at the latest official statistics on union membership. These are produced annually, based on the fourth quarter Labour Force Survey, so the latest report is based on the survey in the last quarter of 2009.
The report includes the 2009 figures for the UK "union wage premium", which is defined as the percentage difference in average hourly earnings of union members with non-members.
Across the UK as a whole, the union wage premium stood at 15.3%, with union members earning an average of £13.60 per hour, compared to £11.80 for non-members, a difference of £1.80 per hour. In just over six hours, this is enough to pay UNITE subs for a whole month!
In the public sector, where 56.6% of employees are union members, union members on average earned 19% more per hour than non-members.
In the private sector, where 15.1% of employees are union members, union members on average earned 5.1% more than non-members.
The fact that the premium exists is a good indicator of the value of union membership. The fact that the premium is so much higher where the proportion of employers who are in the union is higher is a good indicator of the value of strong union organisation.
It is also good to see that the union wage premium rose sharply in both public and private sectors last year, after a fall in 2008 as the recession bit.