One of the really great things about the book The Spirit Level was the way that it showed that inequality impacted badly not just on those at the bottom - but made life worse for pretty much everybody. More equal societies function better was the message.
The authors have returned with a short and fascinating pamphlet.
The central message, that declining union influence has been one of the drivers of rising inequality, isn't exactly new - or something that will have escaped the notice of union members. What is more interesting is the case the authors make about the wider role of unions; that the difference unions make goes far beyond the gains for members in terms of improved wages and conditions.
Unions help influence the wider political climate making fairer and more redistributive tax systems more likely. More than that they help make incomes more equal before taxes. The authors outline a number of examples where strong unions have meant workers get a better share of the economic growth their efforts have produced. This includes political environments which build and support strong public services.
The message is clear - We won't build a fairer society without building stronger Trade Unions.