356 Journal of Reviews on Global Economics, 2013, 2, 356-374 Causality in Economics: A Menu of Approaches Eduardo Pol* School of Economics, Faculty of Business, University of Wollongong, Wollongong, NSW 2522, Australia Abstract: Causality is a notion that occurs often in economics. In using the words ‘cause’ and ‘effect,’ economists seek to distinguish causation from association, recognizing that causes are responsible for producing effects, whereas non- causal associations are not. The identification of causes is accorded a high priority because it is viewed as the basis for understanding economic phenomena and developing policy implications. In this survey we look at different approaches to causality in economics and set out the general principles of each approach, so as to assist in the communication and teaching role. Specifically, we confine attention to five approaches to causality in economics (narrative, comparative statics, theoretical, structural, and experimentalist) and elucidate their distinctive characteristics without entering into philosophical discussions. In particular, we pay close attention to the debate between the structuralist and experimentalist schools because this controversy has been extremely useful to clarify a number of fundamental points concerning causality in economics. Keywords: Causality in economics, causes of effects, counterfactuals, hypotheticals, effects of causes, local average treatment effect. 1. INTRODUCTION effect. It does not necessarily follow from the preceding definition that when the factor in question is absent the Causality is a notion that occurs often in economics. phenomenon does not happen. For example, the In using the words ‘cause’ and ‘effect,’ economists existence of a monopoly provokes a deadweight loss seek to distinguish causation from association, for society as a whole because output would be lower recognizing that causes are responsible for producing than under competition, and probably, the monopolist effects, whereas non-causal associations are not. The would earn abnormal profits. Quite obviously, if identification of causes is accorded a high priority monopoly is nonexistent it does not follow that because it is viewed as the basis for understanding deadweight losses for society are nonexistent. The economic phenomena and developing policy inflation tax, for example, also causes deadweight implications. losses for society, as people waste scarce resources trying to avoid it. The idea that causality is central to economics is at least as old as Adam Smith’s foundational work. Causality (the relation between cause C and effect Indeed, the full title of Smith’s book, An Inquiry into the E) in economics has always been an awkward –and Nature and Causes of the Wealth of Nations, signals elusive– topic. There are at least four sources of that one of the most important tasks of economics is difficulties: first, the use of language with respect to the search for explanations involving causal causality can be very confusing (there is no single connections. The critical question is: how could we definition of causality); second, assuming that we have infer the existence of causal relations from a plausible definition of causality, the definition has to observations? To be sure, the answer to this question be operational (we must be able to test the proffered presupposes a definition of the term ‘cause.’ definition); third, the causality definition should capture the notion of controllability (if there is a cause, it can be The loosest possible definition of ‘cause’ was used to control perhaps in combination with other proposed by Locke (1960:180). Locke’s definition can causes); and finally, when events have several be paraphrased as follows: A cause is a factor that plausible candidate causes, as they usually do in the produces a particular phenomenon called effect. For real economic world, the causality tests tend to be example, what causes long-term inflation? It is difficult to implement. Having said this, it is clear that generally agreed that the rapid growth in the quantity of many economists do not perceive these difficulties as money is the cause of long-term inflation. insurmountable barriers, but as challenges to be The use of the term ‘cause’ can be deceptive when prevailed over. To unravel cause and effect, there are multiple causes that can produce the same economists use common sense, elementary logic, economic models, data, and experiments. *Address correspondence to this author at the School of Economics, Faculty of Business, University of Wollongong, Wollongong, NSW 2522, Australia; Broadly speaking, there are two kinds of causation. Tel: + 61 2 4221 4025; Fax: + 61 2 4221 3725; E-mail: [email protected] First, the analysis may refer to instances of the same E-ISSN: 1929-7092/13 © 2013 Lifescience Global Causality in Economics Journal of Reviews on Global Economics, 2013 Vol. 2 357 phenomenon. The causal analysis of a reproducible above mentioned approaches. For example, time- phenomenon is called general causation. Typical series notions of causality as developed by Granger economic examples of this kind of causality include: the (1969) and Sims (1972) originated an important effects of a firm’s input on its output, the effect of literature that will not be surveyed in this paper only education on earnings, and the effects of employment because of space limitation. Clive Granger (1969) training programs on subsequent labour market offered an operational definition of causality which histories. The second kind of causation analysis turned out to be good enough for many members of the focuses on a dated and non-replicable phenomenon econometrics profession. Granger causality is more a occurring at a particular location such as the financial forecasting technique than a method to detect causes. crisis 1930-33 in the United States. Causation of the A ‘cause’ is identified on the basis of its ability to second kind is said to be singular. In this case, facts do predict an effect.1 not permit the type of replicability that is present in much scientific enquiry. Counterfactual reasoning is The organization of this paper is as follows. There is typically used to explore singular causality. A one section allocated to the description of each counterfactual argument requires the analyst to posit: approach to causality in economics (Sections 2 to 6). In “What would have happened if … had happened (or Section 7 we pay close attention to the debate between not had happened).”Although the general/singular the structuralist and experimentalist perspectives dichotomy occasionally becomes blurred, it helps to because this controversy has been extremely useful to begin by thinking in such terms. clarify a number of fundamental points concerning causality in economics. There is a brief concluding Causality is not only a deep methodological problem section, Section 8, which succinctly summarizes the in economics but also a most complex philosophical menu of approaches. issue. The nature of causality has consumed the attention of philosophers at least since Aristotle, 2. NARRATIVE APPROACH (SMITH) without resolution. For example, Nancy Cartwright (2004) discusses a variety of definitions of causality One of the strongest traditions in economics has from a philosopher’s perspective and argues that been a literary methodology whereby causality causation is not a single, monolithic concept. The problems are explored almost exclusively with words, message send by Cartwright (2004) is that the but without an explicit definition of ‘cause.’ This sort of dominant accounts of causation “do not succeed in causality analysis goes back at least to Adam Smith treating the exemplars employed in alternative (2010). The narrative approach consists of a chain of accounts.” reasoning that it is both theoretical and contextual. In this survey we confine attention to five More precisely, the narrative approach exhibits two approaches to causality in economics and elucidate distinguishing features: first, the approach uses their distinctive characteristics without entering into descriptive economics to provide reasons that certain philosophical discussions. In order to facilitate the factors (say, F1, F2, ... , Fm) provoke a particular effect identification of a particular methodology, we call the E but it is not necessarily based on a comprehensive approaches in question ‘narrative approach (Smith)’, internally consistent formal model showing that when ‘comparative statics approach (Marshall)’, ‘theoretical the factors F1, F2, ... , Fm are present the effect E must approach (Hicks)’, ‘structural approach (Heckman)’, follow; and second, the approach does not have an and ‘experimentalist approach (Angrist-Imbens),’ after explicit definition of ‘cause.’ This approach can be used those individuals most closely identified with the to address causality issues that fall into either category approach. Generally, each approach has its origins of causation (general or singular). further back in time, and is the outcome of research methodologies that have had several contributors apart When there are several causative factors, it is from the named authors. But the references Smith necessary to distinguish ‘separable’ from ‘non- (2010), Marshall (1966), Hicks (1979), Heckman separable’ (candidate) causes. If F is one of the causes (2000), and Imbens and Angrist (1994) are representative of the material, and therefore it appears appropriate to employ the chosen names. 1Somewhat roughly, a variable