Collective actions are actions taken by members of a group to further common interests. Collective action theory can be used to explain the (under-)provision of public goods to solve population health problems
Carlsson (2000) 
Generally, collective action is defined as "actions taken by members of a group to further their common interest" (Bogdanor, 1987, p. 113). This definition, however, narrows the possible appearances of the phenomenon. People can act jointly without common interests, and they can definitely pursue common enterprises outside the realms of formal organizations. Even if we accept the definition, it can be asked whether compatible or complementary interests could also be regarded as "common." We might also contemplate on what the concept of a "group" really means. Thus, the phenomenon collective action is not a unitary concept. This is captured in Figure 1. The matrix illustrates the relation between formal coordination of actors and the extent to which their interests are common.
ODI (Overseas Development Institute) 
Theories of Collective Action
A brief history
Theories of collective action have been puzzled over for centuries. Aristotle himself highlighted the famous ‘Tragedy of the Commons’ when he observed, ‘What is common to the greatest number has the least care bestowed on it’. Today, it is sociologists and economists who have adopted the subject as their own.
In sociology, it was the ‘Group Theorists’ led by Arthur Bentley, who dominated the field at the beginning of the 20th Century (Richardson 1993). Group Theory asserts that where individuals have a common purpose and will benefit from cooperation, a group will form to cooperate for the common good. In the 1960s, this was turned on its head by Mancur Olson’s seminal work, ‘The Logic of Collective Action’ (Olson 1965). His model of the ‘rational’ individual calls into question our willingness to cooperate. Olson suggests that where we believe we can receive the benefits of cooperation without contributing to the cost, we will free-ride and leave the cooperation to others. Most recently, theorists such as Schlozman (1995) have occupied the middle ground. They suggest that we are often motivated to act collectively by our emotions or passion for a cause and that Olson’s definition of rationality is too thin.
In economics, the study of collective action focuses on public goods, common resources and club goods. To some extent, these areas all overlap and can be definitionally hard to separate but the contribution to our understanding of cooperation has been immense. The literature begins with Paul Samuelson’s formal identification of the public goods problem (Samuelson 1947). It continues today with a burgeoning literature on global public goods, prompted by an increasingly ‘globalised’ world with global problems." (p.8)
DIE (German Development Institute) 
Economic theory uses the term collective action to analyse how actors work together in groups in order to achieve common objectives and what problems might impede collaboration (Olson 1965). Collective action theory is used to explain the (under-) provision of public goods and has been extended beyond the nation-state to global collective action and the provision of GPGs (Sandler 2004). This paper will mostly refer to international cooperation and global collective action interchangeably.
Cato Institute 
Language matters. Calling something a “public health problem” suggests that it is different from a personal health problem in ways that demand collective action. And while it doesn’t strictly follow, either in principle or historically, that “collective action” must be state action, that distinction is easily elided in the face of a “public health crisis.”
'Collective action' has been linked to global health problems: "Solving international collective action problems—like tackling pandemics, developing new technologies to control neglected diseases, or strengthening the governance and stewardship of global health systems—is essential for achieving the health-related Sustainable Development Goals (SDGs)."
- Hoffman SJ, Caleo GM, Daulaire N, Elbe S, Matsoso P, Mossialos E, Rizvi Z, Røttingen JA. Strategies for achieving global collective action on antimicrobial resistance. Bulletin of the World Health Organization. 2015; 93: 867-76.
- Lubell, M., Vedlitz, A., Zahran, S., & Alston, L. T. (2006). Collective action, environmental activism, and air quality policy. Political Research Quarterly, 59(1), 149-160. doi:http://dx.doi.org/10.1177/106591290605900113
 Carlsson, L. (2000). Policy networks as collective action. Policy Studies Journal, 28(3), 502-520. doi:http://dx.doi.org/10.1111/j.1541-0072.2000.tb02045.x