Interest groups represent one way for organizations such as firms to manage their external political environments, although in practice many organizations use formal groups as one among a range of strategies with which to influence public affairs. Interest groups range from private groups organizing firms through to public groups open to individuals wishing to join. Organizations are significantly easier to organize than individuals.

The influence of an interest in public affairs depends mainly upon its ability to make itself indispensable by bringing key resources which governments need. Interests in possession of a sufficient quality of these become 'insider' groups with government, and form closed policy-making communities, whereas others find themselves excluded. 'Insider interests' enjoy monopolistic access over public policies, particularly in 'low politics' fields involving relatively technical issues, whereas in 'high politics' fields involving politicized issues they operate on more of a 'level playing field' with other types of interests. 'Outsider' interests therefore seek to disrupt closed 'policy communities' by seeking to politicize issues. A further factor governing the influence of interest representation concerns the extent of crowding, so that in Brussels, for instance, there is now one person working in the 'lobbying' sector for every European Commission official. There are now increasing signs of public authorities seeking to manage their interactions with outside interests.

Justin Greenwood