What explains the contemporary spatial distribution of Muslim communities worldwide? Our study’s contribution is twofold.

First, we investigate the role that ancient trade routes have played in facilitating the spread of Islam. Motivated by numerous case studies on the historical relationship between trade and Islam, we construct detailed data on pre-Islamic trade routes, ports and harbours, and establish that proximity to the pre-600 CE trade network is a significant predictor of today’s Muslim adherence in the Old World.

We conduct the analysis both across and within countries across ethnic groups. Figure 1 below depicts the relationship between current-day Muslim adherence across approximately 3,000 ethnic groups in the Old World and their historical homelands’ proximity to pre-600 AD trade routes and ports. Groups further away from the pre-Islamic trade network are systematically less likely to be Muslim today.

Figure 1. Pre-Islamic trade routes and Muslims across groups in 2005 CE. Conditional on geographic characteristics and country FE

Leveraging within contemporary-states-across-group variation in religious composition is desirable from an empirical point of view as country-level features including the current-day political boundaries and statewide religious policies have arguably influenced the observed cross-country variation in Muslim adherence.

These empirical findings complement a rich body of qualitative work by prominent Islamicists who have extensively discussed the role of long-distance trade, noting both the diffusion of Islam along trade routes and the importance that Islamic scriptures confer on trade-related matters. An innovation of Islam was the practice of direct trade, where Muslim merchants personally carried goods over long distances along the trade routes rather than relying on intermediaries. For example, the acceptance of Islam in most of Inner Asia, Southeast Asia, and Sub-Saharan Africa is known to have occurred primarily through contacts with Muslim merchants. In addition, the highly personal practice of exchange created preference for Muslims to conduct trade with co-religionists. Therefore, merchants converting to Islam enjoyed substantial externalities like access to the Muslim trade network, steady trade flows, and a reduction in transaction costs.

Our second contribution starts from the observation that Islam flourished in very challenging geographical terrains – parts of the world that harboured inherently unequal economic opportunities and often bred conflict. Any political platform that attempted to bring clashing populations together had to address these primordial inequities. Islam was certainly such a movement, and its spread is a prime example of how geography shapes a society’s institutional and social arrangements.

Specifically, we explore whether a region’s ecological similarity to the Arabian Peninsula predicts the presence of Muslim communities. But which are the salient geographic features of the cradle of Islam? The Arabian Peninsula has a distinct geography, mainly consisting of desert and semi-arid landscapes with few pockets of moderate fertility including today’s Yemen and scattered oases in the interior. To capture this distinct landscape, we construct for each country/ethnic homeland the Gini coefficient of land quality for agriculture and uncover that ecological similarity to the Arabian Peninsula (reflected in the degree of inequality in the potential for farming across regions) increases Muslim representation.

But why does a region’s ecological similarity to the Arabian Peninsula matter for the spread of Islam? We discuss various explanations that may rationalise this first-time-documented pattern. We start by establishing that groups residing along geographically unequal territories have a particular production structure (both historically and today) with pasture dominating the semi-arid landscapes and farming taking place in the few relatively fertile regions.

These stark differences in the underlying productive endowments generate incentives to trade but may also lead to conflict. Both instances abound in the historical record. For example, Ibn Khaldun (1377), one of the greatest philosophers of the Muslim world, observed that a crucial factor for understanding the Muslim history is the central social conflict between the primitive Bedouin and the urban society (“town” versus “desert”). Similarly, contemporary scholars have noted that when farmers and herders coexisted in absence of an institutional framework coordinating their activities, their interactions were often conflictual, disrupting trade flows across these territories. We conjecture that the trade-promoting Islamic institutional package with its redistributive economic principles, initially engineered to gain a hearing across tribes residing in the geographically unequal regions of the Arabian Peninsula, was likely to be adopted across similarly challenging geographies.[1]

[1] In Michalopoulos, Naghavi and Prarolo (2016) we explore how the endogenous adoption of economic principles similar to those found in Islam shapes the economic performance of Muslim societies across different stages of development.



  • This blog post is based on the authors’ paper Trade and Geography in the Spread of Islam, Economic Journal, December 2018.
  • The post gives the views of its authors, not the position of LSE Business Review or the London School of Economics.
  • Featured image credit: Photo by Inde, under a CC0 licence.
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Stelios Michalopoulos is an associate professor of economics at Brown University, a research associate at the NBER and a research affiliate of the CEPR. A native of Argos, Greece, Stelios holds a B.A. from the Athens University of Economics and Business and a Ph.D. in economics from Brown University. He has held positions at Tufts, Princeton, Harvard and INSEAD as well as at the Federal Reserve Bank. Stelios is a recipient of the 2015 Excellence Award in Global Economic Affairs from the Kiel Institute for the World Economy and has been recently awarded an NSF grant. His primary research interests lie in the intersection of political economy, growth and development.

Alireza Naghavi is a full professor of economics at the University of Bologna and an adjunct professor at John Hopkins University SAIS Bologna Center. He holds a Ph.D. from University College Dublin. He was the global scientific coordinator of the European Commission’s FP7 project INGINEUS on global innovation networks. His research interests focus on international trade and institutions, and include topic such as intellectual property rights, firm organization, innovation, migration, and the economics of religion.

Giovanni Prarolo is an associate professor of economics at the University of Bologna. His research focuses on political economy, cultural diversity, institutions, economic geography and long term development.