Medieval Cities Through the Lens of Urban Economic Theories

May 2020

Remi Jedwab (George Washington University), Noel D. Johnson (George Mason University), and Mark Koyama (George Mason University)

IIEP working paper 2020-9

Abstract: We draw on theories and empirical findings from urban economics to explore and explain patterns of city growth in the Middle Ages (c. 800-1500 CE). We discuss how agricultural development and physical geography determined the location and size of cities during the medieval period. We also consider the relative importance of economies of scale, agglomeration, and human capital spillovers in medieval cities and discuss how their growth was limited by disamenities and constraints on mobility. We discuss how medieval cities responded to shocks such as the Black Death and describe how institutions became increasingly important in determining their trajectories. Avenues for future research are also laid out.


JEL Codes: R11; R12; R19; N9; N93; N95

Key Words: Medieval Era; City Growth; Urbanization; Food Surplus Hypothesis; Agglomeration Effects; Labor Mobility; Pandemics; Institutions; Europe; Asia

Human Capital Accumulation at Work: Estimates for the World and Implications for Development

February 2020

Remi Jedwab, Asif Islam, Paul Romer, and Robert Samaniego

IIEP working paper 2020-3

Abstract: In this paper, we: (i) study wage-experience profiles and obtain measures of returns to potential work experience using data from about 24 million individuals in 1,084 household surveys and census samples across 145 countries; (ii) show that returns to work experience are strongly correlated with economic development – workers in developed countries appear to accumulate twice more human capital at work than workers in developing countries; and (iii) use a simple accounting framework to find that the contribution of work experience to human capital accumulation and economic development might be as important as the contribution of education itself.

JEL: O11; O12; O15; O47; E24; J11; J31

Keywords: Returns to Work Experience; Returns to Education; Human Capital Accumulation; Economic Development; Labor Markets; Development Accounting

Cities of Workers, Children or Seniors? Age Structure and Economic Growth in a Global Cross-Section of Cities

August 2019

Remi Jedwab, Daniel Pereira, and Mark Roberts

IIEP working paper 2019-13

Abstract: A large literature documents the positive influence of a city’s skill structure on its rate of economic growth. By contrast, the effect of a city’s age structure on its economic growth has been a hitherto largely neglected area of research. We hypothesize that cities with more working-age adults are likely to grow faster than cities with more children or seniors and set out the potential channels through which such differential growth may occur. Using data from a variety of historical and contemporary sources, we show that there exists marked variation in the age structure of the world’s largest cities, both across cities and over time. We then study how age structure affects economic growth for a global cross-section of mega-cities. Using various identification strategies, we find that mega-cities with higher dependency ratios – i.e. with more children and/or seniors per working-age adult – grow significantly slower. Such effects are particularly pronounced for cities with high shares of children. This result appears to be mainly driven by the direct negative effects of a higher dependency ratio on the size of the working-age population and the indirect effects on work hours and productivity for working age adults within a city.

JEL: R10; R11; R19; J11; J13; J14; O11; N30

Keywords: Urbanization; Cities; Age Structure; Dependency Ratios; Children; Ageing; Demographic Cycles; Agglomeration Effects; Human Capital; Growth; Development

The Economics of Missionary Expansion: Evidence from Africa and Implications for Development

May 2019

Remi Jedwab, Felix Meier zu Selhausen, and Alexander Moradi

IIEP Working Paper 2019-10

Abstract: How did Christianity expand in sub-Saharan Africa to become the continent’s dominant religion? Using annual panel data on all Christian missions from 1751 to 1932 in Ghana, as well as cross-sectional data on missions for 43 sub-Saharan African countries in 1900 and 1924, we shed light on the spatial dynamics and determinants of this religious diffusion process. Missions expanded into healthier, safer, more accessible, and more developed areas, privileging these locations first. Results are confirmed for selected factors using various identification strategies. This pattern has implications for extensive literature using missions established during colonial times as a source of variation to study the long-term economic effects of religion, human capital and culture. Our results provide a less favorable account of the impact of Christian missions on modern African economic development. We also highlight the risks of omission and endogenous measurement error biases when using historical data and events for identification.

JEL Codes: N3, N37, N95, Z12, O12, O15

Keywords: Economics of Religion; Religious Diffusion; Path Dependence; Economic Development; Compression of History; Measurement; Christianity; Africa

The Average and Heterogeneous Effects of Transportation Investments: Evidence from sub-Saharan Africa 1960-2010

March 2019

Remi Jedwab and Adam Storeygard

IIEP Working Paper 2019-8

Abstract: Previous work on transportation investments has focused on average impacts in high- and middle-income countries. We estimate average and heterogeneous effects in a poor continent, Africa, using roads and cities data spanning 50 years in 39 countries. Using changes in market access due to distant road construction as a source of exogenous variation, we estimate an 30-year elasticity of city population with respect to market access of 0.06–0.18. Our results suggest that this elasticity is stronger for small and remote cities, and weaker in politically favored and agriculturally suitable areas. Access to foreign cities matters little.

JEL Codes: R11; R12; R4; O18; O20; F15; F16

Keywords: Transportation Infrastructure; Paved Roads; Urbanization; Cities; Africa; Market Access; Trade Costs; Highways; Internal Migration; Heterogeneity

Pandemics, Places, and Populations: Evidence from the Black Death

February 2019

Remi Jedwab, Noel D. Johnson, and Mark Koyama

IIEP Working Paper 2019-3

Abstract: The Black Death killed 40% of Europe’s population between 1347-1352, making it one of the largest shocks in the history of mankind. Despite its historical importance, little is known about its spatial effects and the effects of pandemics more generally. Using a novel dataset that provides information on spatial variation in Plague mortality at the city level, as well as various identification strategies, we explore the short-run and long-run impacts of the Black Death on city growth. On average, cities recovered their pre-Plague populations within two centuries. In addition, aggregate convergence masked heterogeneity in urban recovery. We show that both of these facts are consistent with a Malthusian model in which population returns to high-mortality locations endowed with more rural and urban fixed factors of production. Land suitability and natural and historical trade networks played a vital role in urban recovery. Our study highlights the role played by pandemics in determining both the sizes and placements of populations.

JEL: R11; R12; O11; O47; J11; N00; N13

Keywords: Pandemics; Black Death; Mortality; Path Dependence; Cities; Urbanization; Malthusian Theory; Migration; Growth; Europe

Negative Shocks and Mass Persecutions: Evidence from the Black Death

March 2017

by Remi Jedwab (George Washington University), Mark Koyama (George Mason University) & Noel Johnson (George Mason University)

IIEP Working Paper 2017-4

The authors of this paper examine the Black Death persecutions committed against the Jewish people to demonstrate the factors that determine when a minority group will face persecution. A theoretical framework is developed that predicts that there is an increased probability that minorities are scapegoated and persecuted when negative shocks occur. However, if the shocks become more severe, the probability of persecution may decrease when economic complementarities exist between the majority and minority groups. To accomplish this, the authors gathered data on a city-level on Black Death mortality and Jewish persecution. An aggregate level showed that scapegoating led to an increase in the baseline probability of persecution. On the city-level, high plague mortality rates did not align with increased persecutions. Persecutions were found to be more likely in cities with a history of antisemitism and less likely in locations where Jews were featured in important economic roles.

The Black Death had wide-ranging social effects, and historians and economists often look to the Black Death as a direct cause of scapegoating and persecution of Jewish communities. The authors contradict this view using city-level Black Death mortality rates and Jewish persecution, demonstrating that the higher the mortality in a city, the less likely persecution would occur. This was accentuated in cities where Jews played important economic roles. They show that, while the Black Death shock was the initial impetus for antisemitic persecution in Europe, it was mainly patterns of differences in economic standing between minority and majority groups that explain local variation in persecution.

Their work contributes to several literatures, such as recent work on the economics of mass killings. They also add to literature on the relationship between shocks and the persecution of minorities, which emphasizes the role played by economic complementarities between groups, and literature on antisemitism. Their study provides a unique perspective, as well, as the Black Death provides a very well suited setting to examine the causes of mass killings.

In their framework, negative shocks can increase both the incentive to persecute a minority and to raise that minority’s economic value. The authors conclude that the decision to persecute the minority is dependent upon how the intensity of the shock interacts with the benefit one gains from persecution and the economic benefits gained from the presence of the minority. While their research suggested there are underlying biases against minorities, it also demonstrated that complementary economic activities between minority groups and majority groups could reduce inter-group aggression.

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