There is a very broad picture to be drawn about union organization in Britain across the last twenty-five years. More or less independent of the measure of union organization one takes – and we will discuss several below – there is less of it than there was in 1979. The task for the academic analyst may thus be seen as documenting the decline and attempting explanations for it and, indeed, much of this type of activity has taken place. However, the attempt to explain the decline in union organization has itself indicated the complexity of the phenomenon and the information loss which results if one fails to disaggregate the process of change in trade union organization.