FRANK R. BAUMGARTNER Richard J. Richardson Distinguished Professor of Political Science at the University of North Carolina at Chapel Hill, USASHAUN BEVAN Research Associate in the Institute for Political and Economic Governance, University of Manchester, UK JAN BEYERS Professor in the Department of Political Science at the University of Antwerp, Belgium CAELESTA BRAUN-POPPELAARS Postdoctoral Researcher in the Department of Political Science of the University of Antwerp, BelgiumJAN W. VAN DETH Professor of Political Science and International Comparative Social Research at the University of Mannheim, Germany JAMIE GREENAN graduated with a Masters in Sociology from Aberdeen University in 2004 and subsequently gained a Masters in Social Research in 2005 also from Aberdeen DARREN HALPIN Associate Professor in the Department of Political Science at Aarhus University, DenmarkMARCEL HANEGRAAFF PhD student at the department of Political Science of the University of Antwerp, BelgiumGRANT JORDAN Emeritus Professor, University of Aberdeen, UK DAVID LOWERY Bruce R. Miller and Dean D. LaVigne Professor of Political Science at Pennsylvania State University, USA WILLIAM MALONEY Professor of Politics, Newcastle University, UK IAIN MACLEO Researcher at the Institute for Management, Governance and Society (IMaGeS) at Robert Gordon University, Aberdeen, UKJOHN D. MCCARTHY Professor and Head of the Department of Sociology at the Pennsylvania State University, USAJOHN MOHAN Professor of Social Policy, University of Southampton, UK and Deputy Director of the Third Sector Research CentrePETER MUNK CHRISTIANSEN Professor of Political Science at the Department of Political Science, Aarhus University, DenmarkANTHONY NOWNES Professor of Political Science at the University of Tennessee, Knoxville, USAKAY LEHMAN SCHLOZMAN J. Joseph Moakley Endowed Professor of Political Science at Boston College, USA

• Introduction; D.Halpin & G.Jordan Counting the Voices in the Heavenly Chorus: Pressure Participants in Washington Politics; K.Schlozman Enumerating Populations of Interest Organizations: The Several Theoretical Purposes of Counting; D.Lowery The Changing Contours of British Representation: Pluralism in Practice; G.Jordan & J.Greenan Numbers in a Niche: Lessons from Mapping Gay and Lesbian Groups in the US states; A.J.Nownes Multiple Arenas, Multiple Populations: Counting Organized Interests in Scottish Public Policy; D.Halpin , G.Baxter & I.MacLeod Tracking Interest Group Populations in the US and UK; G.Jordan , F.Baumgartner , J.McCarthy , S.Bevan & J.Greenan The Usual Suspects: Interest Group Dynamics and Representation in Denmark; P.M.Christiansen Mapping the WTO Interest Group System: Exploring Density, Diversity and Stability Over Time; M.Hanegraaff , J.Beyers & C.Braun-Poppelaars Below Which Radar? Mapping the Activities of Unregulated Third Sector Organisations in England; J.Mohan Counting at the Local Level: Where to Stop Counting?; W.A.Maloney & J.W. van Deth Conclusion; G.Jordan & D.Halpin

FRANK R. BAUMGARTNER Richard J. Richardson Distinguished Professor of Political Science at the University of North Carolina at Chapel Hill, USASHAUN BEVAN Research Associate in the Institute for Political and Economic Governance, University of Manchester, UK JAN BEYERS Professor in the Department of Political Science at the University of Antwerp, Belgium CAELESTA BRAUN-POPPELAARS Postdoctoral Researcher in the Department of Political Science of the University of Antwerp, BelgiumJAN W. VAN DETH Professor of Political Science and International Comparative Social Research at the University of Mannheim, Germany JAMIE GREENAN graduated with a Masters in Sociology from Aberdeen University in 2004 and subsequently gained a Masters in Social Research in 2005 also from Aberdeen DARREN HALPIN Associate Professor in the Department of Political Science at Aarhus University, DenmarkMARCEL HANEGRAAFF PhD student at the department of Political Science of the University of Antwerp, BelgiumGRANT JORDAN Emeritus Professor, University of Aberdeen, UK DAVID LOWERY Bruce R. Miller and Dean D. LaVigne Professor of Political Science at Pennsylvania State University, USA WILLIAM MALONEY Professor of Politics, Newcastle University, UK IAIN MACLEO Researcher at the Institute for Management, Governance and Society (IMaGeS) at Robert Gordon University, Aberdeen, UKJOHN D. MCCARTHY Professor and Head of the Department of Sociology at the Pennsylvania State University, USAJOHN MOHAN Professor of Social Policy, University of Southampton, UK and Deputy Director of the Third Sector Research CentrePETER MUNK CHRISTIANSEN Professor of Political Science at the Department of Political Science, Aarhus University, DenmarkANTHONY NOWNES Professor of Political Science at the University of Tennessee, Knoxville, USAKAY LEHMAN SCHLOZMAN J. Joseph Moakley Endowed Professor of Political Science at Boston College, USA

• Introduction; D.Halpin & G.Jordan Counting the Voices in the Heavenly Chorus: Pressure Participants in Washington Politics; K.Schlozman Enumerating Populations of Interest Organizations: The Several Theoretical Purposes of Counting; D.Lowery The Changing Contours of British Representation: Pluralism in Practice; G.Jordan & J.Greenan Numbers in a Niche: Lessons from Mapping Gay and Lesbian Groups in the US states; A.J.Nownes Multiple Arenas, Multiple Populations: Counting Organized Interests in Scottish Public Policy; D.Halpin , G.Baxter & I.MacLeod Tracking Interest Group Populations in the US and UK; G.Jordan , F.Baumgartner , J.McCarthy , S.Bevan & J.Greenan The Usual Suspects: Interest Group Dynamics and Representation in Denmark; P.M.Christiansen Mapping the WTO Interest Group System: Exploring Density, Diversity and Stability Over Time; M.Hanegraaff , J.Beyers & C.Braun-Poppelaars Below Which Radar? Mapping the Activities of Unregulated Third Sector Organisations in England; J.Mohan Counting at the Local Level: Where to Stop Counting?; W.A.Maloney & J.W. van Deth Conclusion; G.Jordan & D.Halpin