Roman Empire road network and today's economic development

What was the impact of the Roman Empire road network on today's economic development?

That's what this article (paper here) tries to find out. The main empirical problems are the confounding or omitted variables.

"A key challenge in identifying the effects of ancient infrastructure is filtering out the effect of underlying (geographic) factors that may have influenced both Roman road density and modern-day outcomes. Another concern is how to separate the effect of ancient infrastructure on economic development from the potential broader influence of the Empire (e.g. via institutional or cultural channels).

We address these issues in several ways. First, we focus exclusively on observations (i) within the boundaries of the Roman Empire, and (ii) that were ‘treated’ by at least one road. By focusing on areas connected to the network, we reduce the risk of omitted variables bias, and the risk that our results convolute the impact from the legacy of Roman rule more broadly (e.g. Landes 1998). To further partial out a potential Roman legacy on contemporary outcomes, we control for country fixed effects as well as language fixed effects, which help us to deal with institutional and within-country cultural variation (e.g. Andersen et al. 2016). Second, based on the literature on Roman road construction and our own formal tests thereof, we control extensively for potential geographic confounders throughout the entire analysis. Third, we exploit a natural experiment."

The natural experiment is twofold. First, the obvious two sides of the Roman border gives them a way of estimate the impact of roads. Secondly, the abandonment of roads in MENA (due to the reintroduction of camel caravans) compared to Europe persistence of roads.

"[Roads are a type of public goods that seems to have had] a persistent influence on subsequent public good allocations and comparative development. At the same time, the abandonment of the wheel shock in MENA appears to have been powerful enough to cause that degree of persistence to break down. Overall, our analysis suggests that public good provision is a powerful channel through which persistence in comparative development comes about."


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