  Mancur Olson's "Logic of Collective Action" predicts that voluntary action
for the common good will only happen in small groups. His theory of the
structure and behaviour of organisations fails to account for the UK Labour
Party's promotion of, rejection and ultimate compliance with its Political
Parties Act (PPERA). I propose a revised computational theory to explain this
behaviour. It negates key tenets of Olson's work: that consumption of a common
good by one member inevitably reduces the quantity available to another and
that negotiation between members does not in general affect a decision to work
for the common good. The approach has application in private and public sector
service design.
