The private solution trap in collective action problems across 34 nations

E Eugene Malthouse (Centre for Decision Research and Experimental Economics, School of Economics, University of Nottingham) C Charlie Pilgrim (School of Mathematics, University of Leeds) D Daniel Sgroi (Department of Economics, University of Warwick) M Michela Accerenzi (Fundación ETEA—Development Institute of Universidad Loyola Andalucía) A Antonio Alfonso (Department of Applied Economics I, University of Seville) R Rana Umair Ashraf (Faculty of Economic Sciences, University of Warsaw) M Max Baard (Environmental Policy Research Unit, University of Cape Town) S Sanchayan Banerjee (School for Government, The Policy Institute, King’s College London) A Alexis Belianin (National Research University Higher School of Economics) S Swagata Bhattacharjee (Jindal School of Government and Public Policy, O.P. Jindal Global University) M Mihir Bhattacharya (Department of Economics, Ashoka University) P Pablo Brañas-Garza (Department of Finance, Loyola Behavioral Lab, Universidad Loyola Andalucía) J Juan-Camilo Cárdenas (Facultad de Economía, Universidad de los Andes) M Miguel Carriquiry (Instituto de Economía, Universidad de la República de Uruguay) S Syngjoo Choi (Department of Economics, Seoul National University) G Gwen-Jiro Clochard E Eduardo Ezekiel Denzon (John Gokongwei School of Management, Ateneo de Manila University) B Bartlomiej Dessoulavy-Sliwinski (Faculty of Economic Sciences, University of Warsaw) G Giorgio Dini (Department of Economics, University of Bologna) L Lu Dong (Southern University of Science and Technology) A Antal Ertl (ELTE Centre for Economic and Regional Studies) F Filippos Exadaktylos (Universidad de Barcelona) E Emel Filiz-Ozbay (Department of Economics, University of Maryland) S Sarah Lynn Flecke (Department of Experimental Psychology, University College London) F Fabio Galeotti (CNRS) T Teresa Garcia-Muñoz (University of Granada) N Nobuyuki Hanaki (Institute of Social and Economics Research, University of Osaka) G Guillaume Hollard (Center for Research in Economics and Statistics, École Polytechnique, Institut Polytechnique de Paris) D Daniel Horn (ELTE Centre for Economic and Regional Studies) L Lingbo Huang (Shandong University) D Doruk İriş (Department of Economics, Sogang University) H Hubert Janos Kiss (ELTE Centre for Economic and Regional Studies) J Juliane Koch (Economics Department at Lund University School of Economics and Management) J Jaromír Kovářík (Departamento de Análisis Económico) O Osbert Kwabena Boadi Kwarteng (Department of Agricultural Economics and Agribusiness, College of Basic and Applied Sciences, University of Ghana) A Andreas Lange (Department of Economics, Faculty of Business, Economics and Social Sciences of the University of Hamburg) M Martin Leites (Universidad de la República de Uruguay) T Thomas Ho-Fung Leung (University of Arizona) W Wooyoung Lim (The Hong Kong University of Science and Technology) M Meike Morren (Department of Marketing, Vrije Universiteit Amsterdam) L Laila Nockur (Department of Psychology and Behavioural Sciences, Aarhus University) C Charles Yaw Okyere (Department of Agricultural Economics and Agribusiness, College of Basic and Applied Sciences, University of Ghana) M Mayada Oudah (Division of Social Science, New York University Abu Dhabi) A Ali I. Ozkes (SKEMA Business School, Groupe de Recherche en Droit, Économie et Gestion, Université Côte d’Azur) L Lionel Page (School of Economics, University of Queensland) J Junghyun Park (Seoul National University) S Stefan Pfattheicher (Department of Psychology, Aarhus University) A Antonios Proestakis (Department of Nutrition and Dietetics Sciences, Hellenic Mediterranean University) C Carlos Ramos (LoyolaBehLAB, Department of Finance, Universidad Loyola Andalucía) M Mapi Ramos-Sosa (Department of Applied Economic Analysis, Universidad de Las Palmas de Gran Canaria) M Muhammad Saeed Ashraf (School of Tourism Management, Hengxing University of Science and Technology) M Muhammad Ryan Sanjaya (Universitas Gadjah Mada, Kabupaten Sleman) R Rene Schwaiger (Department of Banking and Finance, University of Innsbruck) O Omar Sene (Alioune Diop University of Bambey) F Fei Song (Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute) S Sarah Spycher (Department of Management, Technology, and Economics) R Rostislav Staněk (Faculty of Economics and Administration, Masaryk University) N Norman Tanchingco (John Gokongwei School of Management, Ateneo de Manila University) A Alessandro Tavoni (Department of Economics, University of Bologna) V Vera te Velde (School of Economics, University of Queensland) M María José Vázquez-De Francisco (Fundación ETEA—Development Institute of Universidad Loyola Andalucía) M Martine Visser (University of Cape Town) J Joseph Tao-yi Wang W Willy Wang (School of Information, University of Michigan) W Wei-Chien Weng K Katharina Werner (Department of Economics, University of Cologne) A Amanda Wijayanti (Universitas Gadjah Mada, Kabupaten Sleman) R Ralph Winkler (Department of Economics and Oeschger Centre for Climate Change Research, University of Bern) J John Wooders (Division of Social Science, New York University Abu Dhabi) L Li Ying (Institute of Psychology, Chinese Academy of Sciences) W Wei Zhen (Institute of Psychology, Chinese Academy of Sciences) T Thomas Hills (Department of Psychology, University of Warwick)

Abstract

Collective action problems emerge when individual incentives and group interests are misaligned, as in the case of climate change. Individuals involved in these problems are generally considered to have two options: contribute toward public solutions such as global warming mitigation or free ride. However, many collective action problems today involve a third option of investing in a “private solution” such as local adaptation. The availability of this third option can lead to a private solution trap whereby private solutions are adopted, collectively optimal public solutions are not provided, and existing inequalities are exacerbated. We investigated the private solution trap with a collective action game featuring private and public solutions, wealth inequality determined by luck or merit, and participants from 34 countries. We found that the joint existence of private solutions and wealth inequality had a consistent effect across countries: Participants given a higher endowment adopted private solutions almost twice as often as those given a lower endowment, regardless of whether it was determined by luck or merit, and contributed proportionally less toward public solutions. Wealth inequality increased in every country and those given lower endowments were often left unprotected as public solutions were not provided. Across countries, cultural values of hierarchy and harmony were associated with preferences for private and public solutions, respectively. We also identified two universal pathways toward public solution provision: early contributions and conditional cooperation. Our findings highlight the ubiquity of the private solution trap, its cultural underpinnings, and its potential consequences for global collective action problems.

Article Details

Volume / Issue Vol. 123, Issue 12
Published March 24, 2026
ISSN 0027-8424
Publisher National Academy of Sciences

Authors (72)

E

Eugene Malthouse

Centre for Decision Research and Experimental Economics, School of Economics, University of Nottingham

C

Charlie Pilgrim

School of Mathematics, University of Leeds

D

Daniel Sgroi

Department of Economics, University of Warwick

M

Michela Accerenzi

Fundación ETEA—Development Institute of Universidad Loyola Andalucía

A

Antonio Alfonso

Department of Applied Economics I, University of Seville

R

Rana Umair Ashraf

Faculty of Economic Sciences, University of Warsaw

M

Max Baard

Environmental Policy Research Unit, University of Cape Town

S

Sanchayan Banerjee

School for Government, The Policy Institute, King’s College London

A

Alexis Belianin

National Research University Higher School of Economics

S

Swagata Bhattacharjee

Jindal School of Government and Public Policy, O.P. Jindal Global University

M

Mihir Bhattacharya

Department of Economics, Ashoka University

P

Pablo Brañas-Garza

Department of Finance, Loyola Behavioral Lab, Universidad Loyola Andalucía

J

Juan-Camilo Cárdenas

Facultad de Economía, Universidad de los Andes

M

Miguel Carriquiry

Instituto de Economía, Universidad de la República de Uruguay

S

Syngjoo Choi

Department of Economics, Seoul National University

G

Gwen-Jiro Clochard

E

Eduardo Ezekiel Denzon

John Gokongwei School of Management, Ateneo de Manila University

B

Bartlomiej Dessoulavy-Sliwinski

Faculty of Economic Sciences, University of Warsaw

G

Giorgio Dini

Department of Economics, University of Bologna

L

Lu Dong

Southern University of Science and Technology

A

Antal Ertl

ELTE Centre for Economic and Regional Studies

F

Filippos Exadaktylos

Universidad de Barcelona

E

Emel Filiz-Ozbay

Department of Economics, University of Maryland

S

Sarah Lynn Flecke

Department of Experimental Psychology, University College London

F

Fabio Galeotti

CNRS

T

Teresa Garcia-Muñoz

University of Granada

N

Nobuyuki Hanaki

Institute of Social and Economics Research, University of Osaka

G

Guillaume Hollard

Center for Research in Economics and Statistics, École Polytechnique, Institut Polytechnique de Paris

D

Daniel Horn

ELTE Centre for Economic and Regional Studies

L

Lingbo Huang

Shandong University

D

Doruk İriş

Department of Economics, Sogang University

H

Hubert Janos Kiss

ELTE Centre for Economic and Regional Studies

J

Juliane Koch

Economics Department at Lund University School of Economics and Management

J

Jaromír Kovářík

Departamento de Análisis Económico

O

Osbert Kwabena Boadi Kwarteng

Department of Agricultural Economics and Agribusiness, College of Basic and Applied Sciences, University of Ghana

A

Andreas Lange

Department of Economics, Faculty of Business, Economics and Social Sciences of the University of Hamburg

M

Martin Leites

Universidad de la República de Uruguay

T

Thomas Ho-Fung Leung

University of Arizona

W

Wooyoung Lim

The Hong Kong University of Science and Technology

M

Meike Morren

Department of Marketing, Vrije Universiteit Amsterdam

L

Laila Nockur

Department of Psychology and Behavioural Sciences, Aarhus University

C

Charles Yaw Okyere

Department of Agricultural Economics and Agribusiness, College of Basic and Applied Sciences, University of Ghana

M

Mayada Oudah

Division of Social Science, New York University Abu Dhabi

A

Ali I. Ozkes

SKEMA Business School, Groupe de Recherche en Droit, Économie et Gestion, Université Côte d’Azur

L

Lionel Page

School of Economics, University of Queensland

J

Junghyun Park

Seoul National University

S

Stefan Pfattheicher

Department of Psychology, Aarhus University

A

Antonios Proestakis

Department of Nutrition and Dietetics Sciences, Hellenic Mediterranean University

C

Carlos Ramos

LoyolaBehLAB, Department of Finance, Universidad Loyola Andalucía

M

Mapi Ramos-Sosa

Department of Applied Economic Analysis, Universidad de Las Palmas de Gran Canaria

M

Muhammad Saeed Ashraf

School of Tourism Management, Hengxing University of Science and Technology

M

Muhammad Ryan Sanjaya

Universitas Gadjah Mada, Kabupaten Sleman

R

Rene Schwaiger

Department of Banking and Finance, University of Innsbruck

O

Omar Sene

Alioune Diop University of Bambey

F

Fei Song

Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute

S

Sarah Spycher

Department of Management, Technology, and Economics

R

Rostislav Staněk

Faculty of Economics and Administration, Masaryk University

N

Norman Tanchingco

John Gokongwei School of Management, Ateneo de Manila University

A

Alessandro Tavoni

Department of Economics, University of Bologna

V

Vera te Velde

School of Economics, University of Queensland

M

María José Vázquez-De Francisco

Fundación ETEA—Development Institute of Universidad Loyola Andalucía

M

Martine Visser

University of Cape Town

J

Joseph Tao-yi Wang

W

Willy Wang

School of Information, University of Michigan

W

Wei-Chien Weng

K

Katharina Werner

Department of Economics, University of Cologne

A

Amanda Wijayanti

Universitas Gadjah Mada, Kabupaten Sleman

R

Ralph Winkler

Department of Economics and Oeschger Centre for Climate Change Research, University of Bern

J

John Wooders

Division of Social Science, New York University Abu Dhabi

L

Li Ying

Institute of Psychology, Chinese Academy of Sciences

W

Wei Zhen

Institute of Psychology, Chinese Academy of Sciences

T

Thomas Hills

Department of Psychology, University of Warwick