Lateral pressure theory
“Lateral pressure” refers to any tendency (or propensity) of individuals and societies to expand their activities and exert influence and control beyond their established boundaries, whether for economic, political, military, scientific, religious, or other purposes (Choucri and North, 1972; 1975; Ashley, 1980; Choucri and North, 1989; North, 1990; Choucri, North and Yamakage, 1992; Lofdahl, 2000). Framed by Robert C. North and Nazli Choucri, the theory addresses the sources and consequences of such a tendency.
Lateral pressure is a relatively neutral concept similar to what Pitrim Sorokin (1957: 565) called economic expansion and Simon Kuznets (1966, 334-348) referred to more broadly as outward expansion. The strength of a country's lateral pressure is generally taken to correlate positively with its "power" as conventionally understood. The theory of lateral pressure draws on the level of analysis or Image perspective in international relations (Boulding 1956; Waltz (1979) largely as an initial framing and extends this traditional perspective in specific ways.
Lateral Pressure theory seeks to explain the relationships between domestic growth and international behavior. The causal logic runs from the internal drivers, the master variables that shape the profiles of states -- through the intervening effects of socially aggregated and articulated demands and institutional capabilities -- toward modes of external behavior designed to meet demands given the capabilities at hand (Choucri and North, 1989). To the extent that states extend their behavior outside territorial boundaries – driven by a wide range of capabilities and motivations – they are likely to encounter other states similarly engaged. Intersection among spheres of influence is thus the first step of the dynamics leading to conflict and violence. The subsequent developments are contingent on the actors‘ intents, capabilities, and activities. Framed thus, the theory addresses the sources and consequences of transformation and change in international relations.
Choucri and North (1972; 1975) formulated the first phase of the theory of lateral pressure in qualitative as well as quantitative terms. They noted that, in general, the strength of a country's lateral pressure correlates positively with its capabilities and "power" (a concept that is almost universally used but defined with difficulty). Lateral pressure theory provides a more detailed and nuanced view of the sources of power, the types of leverages, manifestations, and the behaviors that can be inferred. It puts forth specific propositions for why certain types of international behaviors or activities appear to be more prevalent in some countries than others. For reviews of the lateral pressure theory see, for example, Levy 2005 ; and Schweller and Pollins, 1999).
Basics of Lateral Pressure Theory 
Framed in multi-disciplinary terms, and drawing on insights and evidence from the social sciences (notably from the natural sciences), the theory and its development over time as a whole can be understood in terms of its specific basic elements, as follows:
Interacting System 
At its origin, the theory assumes all human activity takes place in closely coupled systems, the natural environment and the social domain--an assumption that holds within and across all levels. While the logic of lateral pressure theory argues for their joint or co-dependence (even co-evolution), only social systems are characterized by fully articulated decision systems as we know them. While humans make decisions that have impacts on life-supporting properties, directly or indirectly, the feedback effects are subject to the decision mechanisms of nature. Recent developments focused on the implications of a third, pervasive system of interaction, namely, the cyber system also known as cyberspace with the Internet at its core (Choucri 2012).
The Individual 
Accordingly, the theory adopts an explicitly holistic view, and assumes that the individual as being embedded in the social as well as the natural systems and increasingly in the cyber system. At the core of all social orders are the core activities undertaken by individuals in their efforts to meet their needs and demands aggregated at the level of the society, the state, and the economy, the most fundamental individual needs and wants are driven by the quest for security and survival.
This view of the individual differs from the concept of the First Image in the traditional levels of analysis in international relations as framed, for example, by Waltz (1954). First, the individual is an information processing and an energy using entity. Second, since the theory is anchored in the assumption that homo individualis – in contrast to homo economicus and to homo politicus – situated in an overarching social and natural environment, it is also at odds with the conventional view of economic man, the isolated individual entering an impersonal market at a particular point in time. Further, while both the market and the polity are well understood with respect to properties and modes of behaviors, the traditional view provides an exclusively social view of man. Embedded in the interactive social and natural environments, homo individualis can be an economic, social, or political man, or as others noted further along – depending on role and context at any point in time.
Demands and Capabilities 
Lateral pressure theory assumes that each statistic is an indicator of – and consequence of – a discrete decision by an individual human being governed by his or her preferences. By necessity, individuals made demands on their social and natural environments. The larger the size of the community, the greater are the demands, wants and needs. Population growth, for example, is in fact the outcome of a large number of discrete private decisions (due to volition or to coercion) over which policy makers or national governments are not likely to have direct effective control. In this connection, if there is any ―determinism in this logic, it is one driven by individual decision. Indicators of technology, like those of population, are also the observed outcomes of a number of widely dispersed decisions by individual actors such as developers, inventors, scientists, investors, manufacturers, etc. The same holds for resource access and uses. By the same token, uses of resources begin with meeting individual needs and demands.
Statistics involve descriptions of and generalizations about characteristic features of aggregates. The theory holds that the conceptual transition from the individual to the broader social entity is contingent on societal demands and capabilities.
A demand is a determination that derives from a perceived (or felt) need, want, or desire for the purpose of narrowing or closing the gap between a perception an observed situation (what is) and a preference or value (what ought to be). Basic demands are usually for resource access, better living conditions, physical safety, and security, all of which are generally considered under the rubric of utility by economists; while economists consider demand as the "ability to purchase", lateral pressure theory makes no such assumption. To meet demands -- and to close the gap between the is and the ought to be and possibly approach or establish a preferred condition -- an individuals and societies must possess the required capabilities.
Capabilities consist of the set of attributes that enable performance and allow individuals, groups, political systems, and entire societies to engage in activity to manage their demands. Given that states extensively in their capabilities, their environmental effects will also vary, as will the attendant pressures on the integrity of social systems.
Master Variables 
For purpose of parsimony, the theory assumes that the critical drivers of social activity -- in all contexts and at all levels of development -- can be traced to three interactive master variables– population, resources, and technology. Population involves changes in the size, distribution, and composition of people. Each of these variables can be differentiated along a number of sub-factors or variables – depending on the issues at hand or the interest of the analyst. The same can be said about resources and technology. Technology refers to all applications of knowledge and skills in mechanical (equipment, machinery, etc.) as well as organizational (institutional) terms. This concept of technology encompasses both ―soft‖ and ―hard‖ dimensions, and often the former is as important as the latter. Resources are conventionally defined as ―that which has value‖ to include all elements critical to human existence (such as water, air, etc.), provides a perspective on the concept of resources intimately connected to requisites for basic survival. Each of the master variables is thus obviously not a singular factor but a cluster of constructs (and attendant indicators or sub-variables).
The master variables are the "raw" foundations of the social order.
State Profiles 
Lateral pressure theory argues that all states can be characterized by different combinations of population, resource and technology – the master variables – and that different combinations yield different state profiles – and different impacts on the natural environment. The formal specification of state profiles in the Table below presents the definitional inequality. For convenience, state profiles are displayed in terms of a technology-driven perspective, indicated by the T-variable along the diagonals. But this is not a necessary feature of the theory or of the concept of profiles.
The theory assumes that interactions among these variables within states affect power distributions and relations among states. Different state profiles – characterized by different population/resource/technology relationships -- manifest different propensities for external behaviors (Choucri and North 1990; 1995; North, 1990; Wickboltd and Choucri 2006), Further, that the state profile is a good predictor of power-indicators on the one hand and the attendant environmental effects on the other (Choucri and North 1993).
|*The selection of technology in diagonals is simply because it is the more readily manipulable by public policy than are the other two variables.|
A reorganization of each profile location in this table yields, by definition, a population-driven display, or alternatively, a resource-driven display (each with the P or the R variables along the diagonals) See Choucri and North (1993) and Lofdahl (2002) for the original specification; and Wickboldt and Choucri (2006) for extension of the logic to differentiate empirically among countries within each profile group.
In lateral pressure terms, the generic governance problem can be defined as one of balancing the demands or loads on the system against the deployment of available capacities or institutional capabilities. The theory argues that governance mechanisms and the institutions of the sovereign state protect the system-sustaining properties that ―manage‖ interactions among the elements and entities of the society from the potential instabilities due to system-threatening condition.
The dilemma of governance, in this case, as in all others, is that efforts to meet demand -- or to expand capacity for purposes of meeting demands -- often creates unintended consequences that may undermine the government‘s own position. Thus, the management of demands and capabilities is the intervening process relating state profiles and their characteristics features to propensities for external behavior.
International Relations 
To the extent that states extend their behavior outside territorial boundaries, –they are likely to encounter other states similarly engaged. By definition, international relations consist of interactions among sovereign entities, intergovernmental organizations, non-state entities, such as firm, non-governmental organizations etc. As a result the sovereign state is embedded in a wide range of networks, formal and informal. To simplify, competition for power and influence is a common feature of politics among nations.
The theory argues, and empirical evidence shows, that intersections among spheres of influences—when one state seeks to expand control over the domains of another state -- inevitably fuel prevailing hostilities and reinforce an emerging dynamics of military competition that historically has led the well known phenomenon of arms race. Here the theory draws on four important concepts in international relations theory broadly defined. These are the conflict spiral (such as Holsti 1972); and the arms race dynamics (pioneered by Richardson 1960a); and the security dilemma (notably Herz 1950, Jervis 1997).
The fourth concept is less understood but equally important is the peace paradox (often a feature of the peace system, Choucri in collaboration with North 1975), namely that initiatives by one of the adversaries to reduce hostilities, and de-escalate violence – to make peace signals – could be considered by the other as a sign of weakness and thus an opportunity for taking the offensive and making a move to gain advantage.
Less fully developed in lateral pressure theory are the dynamics of international cooperation. Accordingly, it draws upon concepts of multilateralism, as a form of coordinated behavior among states designed to reduce disorder and anarchy in the international system. Stated differently, as coordinated action among sovereign states, multilateralism emerged as a means of protecting the interests and activities of states in the international system –in their pursuit of wealth and of power (Gilpin 1987).
The Global System 
Lateral pressure theory extends the traditional levels of analysis by positing the global system as an overarching concept that encompasses its constitutive features -- the individual, the state, and the international system – embedded in social and the natural environments. The theory also views globalization in overarching terms -- as fundamental transformations in economic and social structures and processes worldwide set in motion by the large-scale movements of people, resources, and technologies across boundaries. These movements influence the nature of national societies and economies and, under certain circumstances, may even alter them in fundamental ways. Inevitably, they also shape and reshape international exchanges and interactions. To the extent that these processes are sufficiently pervasive and call for changes in dominant policy thrusts, it is reasonable to argue that the essence of globalization lies in the forging of common and overlapping policy spaces.
Phases of Theory Development - Modeling and Simulation 
The development of lateral pressure theory and its empirical underpinnings have gone through several phases. The first phase consists of (a) large scale cross-national statistical econometric investigations of the 45 years leading to World War I and follow-up studies, and (b) detailed complex quantitative inquiry into the political economy of war and peace in Sino-Soviet-US relations during the decades following World War II .
Nations in Conflict a comparative and quantitative analysis of major powers in world politics over four decades prior to World War I (Choucri and North 1975) – includes a set modeling and simulations that yielded of the empirical connections between the master variables and the behavior of states. Choucri and North (1975) developed an econometric simulation model of six major powers over the span of 45 years leading to World War I. In each case they found the causal connection between the master variables and the overt international behavior. The traditionally dominant power during this period, Great Britain, viewed any significant growth in other powers as a source of threat and these perceptions were translated into specific policies intended to retain an advantage over the other powers, most notably a rapidly growing and newly unified Germany.
The Political Economy of War and Peace examines the conflict dynamics in interstate relations among competing powers generated by differentials in growth of population, resource access, and levels of technology (Ashley 1980). Focusing on three major powers during the post World War II decades, the United States, the Soviet Union, and China, it demonstrates the close interconnections among national growth, bilateral rivalry, and multilateral balance of power. The study shows how the dynamics of insecurity and the antagonizing processes contribute to the globalization of military competition which, in turn, creates serious impediments to the collective management of many dimensions of growth itself. Despite changes in world politics since 1914, and the dynamics modeled in Nations in Conflict, some fundamental features of lateral pressure retain powerful resonance during the post World War II war period. This general observation is then followed by careful model development, empirical grounding and parameter estimation as well as simulation of sensitivity analysis. The focus in this case is the overall security problematic on a worldwide basis.
(In retrospect, despite the end of communism and the dissolution of the Soviet Union the analysis as well as the results shed important light on the emergent challenges to global and national security in the 21st century. The unquestionable dominance of the United States in world politics does little to dampen the perceptions of threat due to China‘s growth or Russia‘s competitive intents given its existing capabilities.)
The second phase of lateral pressure modeling is illustrated by a detailed analysis of the case of Japan over the span of more than one hundred years (Choucri, North, and Yamakage 1992). Focusing on growth, development, competition, warfare, and reconstruction Japan illustrated the ways in which a state sought to manage its resource constraints, adopt internal and external policies to meet its core demands, and find itself engaged in competition and conflict it viewed as essential for its survival. The concept of state profile, introduced in an earlier study (Choucri and North 1989), was operationalized and put to the empirical test in the Japan case across three historical period, before World War I, during the Inter-War decades, and following the Second World War.
The Japan case indicates how a country‘s profile can change over time and how these changes are associated with different patterns of international behavior. Each period demonstrated different structural features and alternative pathways for adjustments to internal and external constraints. Examining the Japan case from the Meiji Restoration, through World War I and World War II, and the early 1980s, it was clear that Japan‘s profile continued to demonstrate powerful resource scarcities, and thus the continued dependence on external trade. The demand for imports could only be met by the supply of exports, thus shaping a vicious cycle of reliance on external resources. Japan was caught between a rock (invariant resource levels) and a hard place (external constraints on resource access). In the decades preceding major international conflicts Japan fostered its eventual technology-dominant profile enabling it to engage in a wide range of expansionist activities to reduce its resource constraints.
The third phase of lateral pressure modeling builds on exploratory system dynamics modeling since the 1970s. Early system dynamics models of lateral pressure such as Choucri, Laird, and Meadows (1972) addressed the interconnections among the master variables that create internal sources of external conflict. Extending this work, Choucri and Bousfield (1978) developed a model of the economy anchored in the master variables, and then located sources of lateral pressure and propensities toward modes of external behavior.
Later, in a comparative analysis of 20 countries (industrial and developing) Wils, Kamiya and Choucri (1998) extended the analysis of internal sources of international conflict, and examined the nature of the feedback effects, namely how international conflict in turn influences and even alters the master variables of the state and changes the internal sources of conflict as well as propensities for particular modes of external behavior. Subsequently, Lofdahl (2002) modeled the relationship between internal dynamics of growth and development rooted in the master variables, on the one hand, and propensities toward particular patterns of international trade and their environmental impacts, on the other.
The fourth phase concentrates on the measurement of change in the master variables and implications for international relations. The focus is on the resulting distribution of states both within and across profiles (Wickbolt and Choucri 2006). Using fuzzy logic, made it possible to investigate more systematically and more accurate the distribution of states throughout the international system. This could be an important step in anticipating conflict-prone behavior. Also in this phase are some nascent efforts to conceptualize state behavior in cyberspace, and thus develop metrics to explore propensities for behaviors in cyberspace. Clearly an exact comparison between behaviors in ―real and virtual domains cannot be assumed. Considerable exploratory investigations are required.
All of these initiatives are informative in their own right. Each one provides important insights and evidence about the antagonizing processes that lead to system-threatening dynamics and, in some cases, to overt conflict, violence and war.
- Ashley, Richard A. The Political Economy of War and Peace: The Sino-Soviet-American triangle and the modern security problematique. New York: Nichols Publishing,
- Choucri, Nazli. Cyberpolitics in International Relations. Cambridge, MA: MIT Press, 2012. (in press)
- Choucri, Nazli and Daniel Goldsmith. "Lost in cyberspace: Harnessing the Internet, international relations, and global security." Bulletin of the Atomic Scientists 68 (2) pp. 70-77, (2012).
- Choucri, Nazli, in collaboration with Robert C. North. "In Search of Peace Systems: Scandinavia and the Netherlands, 1870-1970," in Bruce Russett, ed., Peace, War, and Numbers, Berkeley: Sage Publications, 239-74. 1972.
- Choucri, Nazli, Laird, Michael, and Meadows, Dennis. "Resource Scarcity and Foreign Policy: A Simulation Model of International Conflict." Cambridge, MA: MIT Center for International Studies, 1972.
- Choucri, Nazli, and Robert C. North. "Lateral pressure in international relations: Concept and theory." In Handbook of War Studies, edited by Manus I. Midlarsky, 289-326. Ann Arbor: University of Michigan Press, 1989.
- Choucri, Nazli, Robert C. North, and Suzumu Yamakage. The Challenge of Japan before World War II and After: A Study of National Growth and Expansion. London: Routledge, 1992.
- Choucri, Nazli, and Robert C. North. Nations in Conflict: National Growth and International Violence. San Francisco: W. H. Freeman, 1975.
- Herz, John H. "Idealist Internationalism and the Security Dilemma." World Politics 2, no. 2 (1950): 157-180.
- Jervis, Robert. System Effects: Complexity in Political and Social Life. Princeton, NJ: Princeton University Press, 1997.
- Levy, David L. and Peter J. Newell, eds. The Business of Global Environmental Governance. Cambridge, MA: The MIT Press, 2005.
- Lofdahl, Corey L. Environmental Impacts of Globalization and Trade: A systems study. Cambridge, MA: The MIT Press, 2002.
- Ole, Holsti R. Crisis, escalation, war. Montreal: McGill-Queens University Press, 1972.
- Pollins, Brian M., and Randall L. Schweller. "Linking the Levels: The Long Wave and Shifts in U.S. Foreign Policy, 1790-1993." American Journal of Political Science 43, no. 2 (April 1999): 431-464.
- Waltz, Kenneth. Theory of International Politics. New York: McGraw-Hill, 1979.
- Wickboldt, Anne-Katrin and Nazli Choucri. "Profiles of States as Fuzzy Sets: Refinement of Lateral Pressure Theory." In International Interaction.
- Wils, Annababette, Matilde Kamiya and Nazli Choucri. "Threats to sustainability: Simulating conflict within and between nations." System Dynamics Review 14, no. 2-3 (Fall 1998): 129-162.