The Systems Theory: David Easton's Input-Output Model (Explained)

The Systems Theory Approach in Political Science

A system is a set of elements in interaction. The interactions among its elements, between itself and its environment, and the interactions between each of its elements and the environment constitute its dynamics, its adaptive behavior, and its functions.

Simply put, a system is an organized whole in dynamic interaction. A system is a group of parts working together in a regular relationship.

Every political system shows qualities and features similar to those of biological and other systems. Every political system is an organized whole in dynamic interaction. These patterns of interactions produce results that are authoritative and binding.

One of the most important social-scientific formulations of systems theory is the construct of Talcott Parsons. His work has become central to sociology and social science.

Functions of Systems Approach

According to Talcott Parsons, there are four essential functions that any social system must fulfill if it is to preserve its own stability and survival.

  • Pattern maintenance: the preservation or reproduction of a system's pattern or essential characteristics;
  • Function adaptation, which pertains to a system's ability to cope with its environment;
  • Function of goal attainment: the achieving of whatever goals the system may possess. At a minimum, the system will have the goal of survival.
  • Function of interaction, which requires that the various parts and functions of the system cohere and provide a goal of balance among the groups.

David Easton's Input-Output Model of Systems Theory

Input-output analysis: David Easton (1971) is one of the foremost political scientists who has applied a systemic approach to political analysis. The Canadian-born American political scientist regards the political system as a system of interaction within its environment. It deals with a constructive system rather than a natural system such as a biological system.

This means that any set of variables or factors selected for description and explanation constitutes a system, at least for the purposes of basic research. We should note the difference between a membership system, which is made up of human groups, and an analytical system, which is an abstraction that focuses on selected elements of human behavior, e.g., the political system, the economic system, religion, ecology, international, and environmental. Analytical systems are important for research in political science.

The political system is therefore an analytical system existing within the overall membership system formed by a society. It is that system of interaction in any society through which binding or authoritative allocations are made and implemented.

David Easton's Input-Output model

Some of the support interests involve tax actions promoting the goals, interests, and actions of another person, such as a vote for a political candidate or a defense of a decision by the highest court of the land. We have gatekeepers such as the political parties; they are responsible for processing some of the demands made by the input so that the system should be able to contain all the demands without the system collapsing. Note that no political system can process all the demands. Some of the inputs that strive to enter the political system may stop along the way. Sometimes the sub-systems allocate the values demanded by the input so that only a very few of all the inputs get into or enter the political system.

The legislature and other organs help to process some of the demands that have reached the system and give out or allocate values by means of the output law or policy. For any political system to survive, it must be able to aggregate demands made in it, process them, and give out, by way of policy, its verdict. It must also make sure that these policies are implemented.

Types of Demand Input

  • Demands for goods and services, e.g., wages and salary increases, education, roads, light, etc.
  • Demands for regulation of behavior, e.g., public safety, labor relations
  • Demand for participation in the political system. e.g., delegation to the government complaining of a lack of representation in government and other organizations, boards, etc.
  • Symbolic Demand: demand to be chairman, etc

Types of Support Input

  • Material Support: payment of taxes, obedience to the laws and regulations, participating in things like voting
  • Manifestation of deference to people in authority.

Types of Output

  • Extraction: The government extracts money from people, organizations, and all whatnot.
  • Regulation of behavior
  • Allocation of goods and resources, water supply, etc.
  • Symbolic output, e.g., independence anniversary celebration, etc.

Whereas a theory makes empirical knowledge claims, an analytic conceptual scheme is little more than a non-theoretical classificatory tool.

Easton refers to his systems analysis as "a conceptual framework," i.e., a preliminary to the development of theory, and as a way of framing questions and possibilities for seeking answers rather than providing actual answers. It is therefore a way of stimulating thought and a means of classification.

Advantages of Systems Theory

It provides possibilities for organizing collections of empirical evidence into a coherent framework or system. It directs attention from formal and legal institutions, such as constitutions, governments, and international organizations, to defined processes, structures, and the entire system. The criteria of Easton, for example, provide a structured series of questions that can be used to assess the state of an entire system.

John Burton notes that systems theory makes it possible to break down society into sets of relations that are susceptible to orderly, step-by-step analysis of detail without losing sight of the whole. By focusing on these functions, we can determine a great deal about system behavior.

Critique of David Easton's input-output approach

Easton's theory is the most inclusive systemic approach for political analysis. His approach focuses on national political systems, which also constitute international relations.

It also serves as a framework for organizing and conceptualizing data. This is no mean achievement, yet it is one that falls short of a general theory of politics.

Every political system performs the same input and output functions. But systems can be differentiated in terms of the strictures they possess for performing these functions.

Input Functions:

  • Political sociololization
  • Interest articulation, i.e., identification of demands and their transmission from society to the authoritative decision-makers.
  • Interest aggregation
  • Political communication

Output Functions:

  • Rule-making
  • Rule application
  • Rule adjudication


Almond's structural-functional approach is more applicable to comparative politics, in which the various kinds of political systems (democratic, authoritarian, and totalitarian) are composed, than to the international political system. It shares with Easton's approach the tendency to distort reality in the interests of conceptual neatness. It is static in analysis, and one can rationalize status quo patterns through its efforts to demonstrate the functionality of existing arrangements.

Utility of Systems Theory

The construct provides a conceptual framework but not an actual theory.

Merits of David Easton Systems Theory

  • It provides a framework for comparing political systems. Theoretically, the systems approach is not limited to nation-states alone, as there are political systems in unions, clubs, and other organized associations in society.
  • It provides a standardized set of concepts, such as inputs and outputs, to describe activities that take place in all political systems. As such, they can be compared.
  • The approach takes cognizance of the inevitability of change and addresses itself to how the system can adapt itself and survive when faced with changes. This is particularly useful for studying African, Asian, and Latin American societies, which continuously undergo rapid changes resulting from the process of development.
  • By drawing attention to the external environment of every political system, it is a useful approach for analyzing the international political system, especially the linkage between the domestic and international environments.

Criticism of David Easton's Systems Theory

Disadvantages and negative attributes of the systems approach include: 

  • The most popular criticism is that the approach is ideologically oriented towards retaining the status quo. By laying emphasis on order and system maintenance, the approach is not well suited to studying revolutionary changes. In fact, some authors have argued that the approach seeks, from a Western ideological standpoint, to be an alternative approach to Marxism, which suggests that only revolutionary changes can bring about desired changes in society.
  • The approach fails to give a clear definition of what is political, and what differentiates political interactions from other types of social interactions. It seems to assume that all political interactions are directed towards the "authoritative allocation of values." Such emphasis seems to imply that politics only takes place in the national political system. This criticism can, however, be mitigated by the fact that the systems model can be applied to any political system, insofar as the analyst defines its boundaries.
  • The approach seems to suggest that all parts of the political system are equally important. This is, however, untrue because some parts are more important than others, and in any case, different parts perform similar functions in different political systems. This means, for example, that the functions performed by the political parties in the United Kingdom may be performed by the military in Nigeria. Rather than generalize, as the systems approach seems to suggest, the analyst is required to specify which parts are crucial in a particular system and how they affect and are, in turn, affected by others.

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