roman roads to prosperity: the long&run impact of transport

Roman roads to prosperity

Roman Roads to Prosperity:The Long-run Impact of Transport Infrastructure

C-J Dalgaard Nicolai Kaarsen Ola Olsson Pablo SelayaU Copenhagen & U Gothenburg

Linneaus University, April 17, 2015

Dalgaard et al Roman roads

Roman roads to prosperityIntroductionBackgroundEmpirical analysis

Timgad, Algeria, 100 CEDalgaard et al Roman roads

Research questions

What is the causal impact of infrastructure on economicdevelopment?

Typically hard to determine given joint endogeneityRoads and railways often constructed to link alreadyeconomically active communitiesBut communities and economic activity often also emerge afterthe construction of infrastructure

Most evidence suggests infrastructure is strongly associatedwith economic development

Research questions

Typically hard to determine given joint endogeneity

Roads and railways often constructed to link alreadyeconomically active communitiesBut communities and economic activity often also emerge afterthe construction of infrastructure

Research questions

Typically hard to determine given joint endogeneityRoads and railways often constructed to link alreadyeconomically active communities

But communities and economic activity often also emerge afterthe construction of infrastructure

Research questions

Europe at night

Previous literature I

Roman economy: Finley (1973), Temin (2013)

Roman roads in:

Britain (Codrington, 1918; Margary, 1977; Bishop, 2014)Italy (Laurence, 1999); Road construction in Italy part of abroader Roman agenda aimed at political hegemony byshowing persistence and mastery of nature and geography

Legacy of Roman era in Britain and France (Michaels andRauch, 2014)

Path dependency in economic history (North, 1990)

Roman roads in:

Britain (Codrington, 1918; Margary, 1977; Bishop, 2014)

Italy (Laurence, 1999); Road construction in Italy part of abroader Roman agenda aimed at political hegemony byshowing persistence and mastery of nature and geography

Roman roads in:

Previous literature II

Impact of infrastructure:

Railroads in China (Banerjee et al, 2013) during 20th centuryRoads in Brazil after founding of Brasilia (Bird and Straub,2013)Railroads (Fogel, 1962) and highways (Michaels, 2008;Fernald, 1999) in United States

Lights intensity as proxy for economic development

Henderson et al (2013)

Railroads in China (Banerjee et al, 2013) during 20th century

Roads in Brazil after founding of Brasilia (Bird and Straub,2013)Railroads (Fogel, 1962) and highways (Michaels, 2008;Fernald, 1999) in United States

Railroads in China (Banerjee et al, 2013) during 20th centuryRoads in Brazil after founding of Brasilia (Bird and Straub,2013)

Railroads (Fogel, 1962) and highways (Michaels, 2008;Fernald, 1999) in United States

Ideal natural experiment

Random location of roads on a populated but relativelyundeveloped territory

How does this alter the geography of economic activity andhuman settlements?

What is the treatment e¤ect after 1 year, 100 years, or 1000years?

Our paper

Roman road construction during antiquity close to a naturalexperiment

Using geo-coded data on Roman road locations in Europe, weanalyze their impact on current levels of economicdevelopment (historical urban population, conetemporarylights intensity and population density)Identi�cation:

Strong Roman preference for straight roads...built mainly for military purposes...in newly conquered areas, as an exogenous intervention inthe existing geography, giving an "infrastructural treatment"to an undeveloped territory

Main empirical result: A persistent positive e¤ect of Romanroads on historical city population and on current levels onlights intensity

Our paper

Roman road construction during antiquity close to a naturalexperimentUsing geo-coded data on Roman road locations in Europe, weanalyze their impact on current levels of economicdevelopment (historical urban population, conetemporarylights intensity and population density)

Identi�cation:

Our paper

Roman road construction during antiquity close to a naturalexperimentUsing geo-coded data on Roman road locations in Europe, weanalyze their impact on current levels of economicdevelopment (historical urban population, conetemporarylights intensity and population density)Identi�cation:

Our paper

Strong Roman preference for straight roads

...built mainly for military purposes

...in newly conquered areas, as an exogenous intervention inthe existing geography, giving an "infrastructural treatment"to an undeveloped territory

Our paper

Strong Roman preference for straight roads...built mainly for military purposes

...in newly conquered areas, as an exogenous intervention inthe existing geography, giving an "infrastructural treatment"to an undeveloped territory

Our paper

Our contribution

An identi�cation based on i) straight roads, ii) militarypurpose, iii) construction in uncivilized, newly conqueredterritories

Time span of 2000 years

First quanti�cation of importance of Roman roads forEuropean development

Within-country variation in a sample of pixel cells

Our contribution

Brief history

Republic 500-30 BCE, peak era 100-200 CE whenMediterranean is a Roman lake

Conversion to Christianity in 312 CE, large barbarian invasionsfrom 375 BCE,

Western Rome collapses in 476 CE

Dark Ages 476-800, strong Western revival from about 1100

Byzantium (Constantinople) remains a signi�cant power untilit was defeated by the Ottomans in 1453

Brief history

Via Appia

First paved road Via Appia (Appian Way) in 312 BCE

During Second Samnite War 327-304, Roman armies weretrapped around Capua due to shortage of supplies from Rome

Censor Appius Claudius starts building Via Appia southwardsto Capua in 312 as well as Aqua Appia to supply Rome withwater

With new and more e¢ cient supply lines, Romans defeat theSamnites in 304

Road extended to Beneventum in 290 and to Brundisium in264

Downside: King Pyrrhus marches along Via Appia from southand threaten Rome in 280-275

Via Appia

Via Appia (312-264 BCE)

Via Aemilia (187 BCE)

Roads in Roman empire 117 CE

Construction

Types of roads:

Viae publicae - public highways or main roads, typicallyordered by censors, and administered by curatores, mainly amilitary responsibilityViae privatae - private or country roads, often originallycreated and �nanced but by wealthy individualsViae vicinales - roads between villages or within districts,linking to other roads

Roads also required bridges, milestones, guest houses, tunnels,drainage systems, etc

Road tolls on bridges and city gates, an o¢ cial imperial mailsystem cursus publicus created by Augustus

In total, 80 000 kms of paved road in empire at its peak

Construction

Types of roads:

Viae publicae - public highways or main roads, typicallyordered by censors, and administered by curatores, mainly amilitary responsibility

Viae privatae - private or country roads, often originallycreated and �nanced but by wealthy individualsViae vicinales - roads between villages or within districts,linking to other roads

Construction

Types of roads:

Viae publicae - public highways or main roads, typicallyordered by censors, and administered by curatores, mainly amilitary responsibilityViae privatae - private or country roads, often originallycreated and �nanced but by wealthy individuals

Viae vicinales - roads between villages or within districts,linking to other roads

Construction

Types of roads:

Construction

Types of roads:

Construction

Types of roads:

Construction

Types of roads:

Construction

Straight roads between two points in order to economize oncosts

Points could be existing cities (Rome-Capua for Via Appia) ora border, river, or another road

Straight roads not "optimal" from a traveller�s perspective(crossing steep slopes, marshes, forests, etc)

Often constructed in "uncivilized" territory withoutpredecessor roads (particularly in the western parts)

Hence, close to a random "road treatment"

Construction

Example

Endogenous to development

Typical Roman choice

Economic impact

Short term:

Stronger presence of Roman military and colonistsGreater security and stability lead to investmentsDivision of labor, trade and agriculture expand, creating citiesand urban hinterlandsTechnological di¤usion

Medium term:

Even during the Dark Ages 476-800 CE, Roman roads one offew functioning modes of communicationPath dependency in urban systemsCertain road re-orientation to take into account new nationalboundaries and industrial production

Economic impact

Short term:

Stronger presence of Roman military and colonists

Greater security and stability lead to investmentsDivision of labor, trade and agriculture expand, creating citiesand urban hinterlandsTechnological di¤usion

Medium term:

Economic impact

Short term:

Stronger presence of Roman military and colonistsGreater security and stability lead to investments

Division of labor, trade and agriculture expand, creating citiesand urban hinterlandsTechnological di¤usion

Medium term:

Economic impact

Short term:

Stronger presence of Roman military and colonistsGreater security and stability lead to investmentsDivision of labor, trade and agriculture expand, creating citiesand urban hinterlands

Technological di¤usion

Medium term:

Economic impact

Short term:

Medium term:

Economic impact

Short term:

Medium term:

Economic impact

Short term:

Medium term:

Even during the Dark Ages 476-800 CE, Roman roads one offew functioning modes of communication

Path dependency in urban systemsCertain road re-orientation to take into account new nationalboundaries and industrial production

Economic impact

Short term:

Medium term:

Even during the Dark Ages 476-800 CE, Roman roads one offew functioning modes of communicationPath dependency in urban systems

Certain road re-orientation to take into account new nationalboundaries and industrial production

Economic impact

Short term:

Medium term:

Economic impact

Long term:

Some persistence of economic and population patterns

Hypothesis: Positive (reduced-form) e¤ect of road intensity on

Historical levels of city population 1300-1850Current population densitiesCurrent economic activity (measured as lights at night viewedfrom satellites)

Economic impact

Long term:

Economic impact

Long term:

Economic impact

Long term:

Historical levels of city population 1300-1850

Current population densitiesCurrent economic activity (measured as lights at night viewedfrom satellites)

Economic impact

Long term:

Historical levels of city population 1300-1850Current population densities

Current economic activity (measured as lights at night viewedfrom satellites)

Economic impact

Long term:

Preliminary evidence: Major cities 1450

Major cities and roads 2014

Data: Roman roads

Data on Roman roads constructed by scanning the BarringtonAtlas of the Greek and Roman World (2000), presented atwebsite Digital Atlas of Roman and Medieval Civilizations(http://darmc.harvard.edu/)

Measured at peak of empire at the death of Trajan 117 CE

Only "certain" roads in sample

Measurement:

Create bu¤ers of various width around a road (10 m up to 10km)Bu¤er area as a fraction of total area of grid cell or region

Data: Roman roads

Measurement:

Data: Roman roads

Measurement:

Data: Roman roads

Measurement:

Data: Roman roads

Measurement:

Create bu¤ers of various width around a road (10 m up to 10km)

Bu¤er area as a fraction of total area of grid cell or region

Data: Roman roads

Measurement:

Barrington Atlas (2000)

Dependent variable and covariates

Dependent variables are:

Historical city population levels (Bairoch 1988; Nunn andQian, 2012), cities with a population>1000Average current light intensity at night (NASA, 2012)Current population (Rappaport and Sachs, 2003)

Standard sources for other covariates

Control variable sets: Location (distance to Rome, distance toborder), Climate (latitude, precipitation, temperature), Geo(distance coast or river, distance to ocean, roughness ofterrain, elevation, area)

Historical city population levels (Bairoch 1988; Nunn andQian, 2012), cities with a population>1000

Average current light intensity at night (NASA, 2012)Current population (Rappaport and Sachs, 2003)

Historical city population levels (Bairoch 1988; Nunn andQian, 2012), cities with a population>1000Average current light intensity at night (NASA, 2012)

Current population (Rappaport and Sachs, 2003)

Unit of analysis

Due to potentially endogenous borders, our main unit ofanalysis are constructed grid cells 1x1 lat-long degrees

Mean area inside Roman empire: 5111 kms (85x111 kms)

972 pixel cells

Bu¤er zone: 500 m on either side

Unit of analysis

972 pixel cells

Unit of analysis

972 pixel cells

Unit of analysis

972 pixel cells

Pixel cell: Ile de France

Lights and roads in grids: Roman empire

Geographical determinants of roads

log (RRp) = X0pγ+ εp

RRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls (distance to: ocean, river,border, Rome; Eastern empire dummy)εp is an error term

RRp is our Roman road indicator (either a dummy or acontinuous variable)

Xpt is set of geographical controls (distance to: ocean, river,border, Rome; Eastern empire dummy)εp is an error term

RRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls (distance to: ocean, river,border, Rome; Eastern empire dummy)

εp is an error term

RRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls (distance to: ocean, river,border, Rome; Eastern empire dummy)εp is an error term

Determinants of Roman roads

Table 1: Roman road (0/1)(1) (2) (3)

DV: Roman roadDist. major river -0.00Dist. ocean 0.00Latitude 0.01Dist. border -0.00Dst. Rome -0.00Eastern Rome -0.21***Time since Neo. -0.00*** 0.00Sample All All No E. RomeObs 969 220 159R2 0.152 0.04 0.00

Robust s.e. *** p<0.01, ** p<0.05, * p<0.1

Econometric speci�cation: Historical analysis

log (upt ) = dt + δp +∑t�1200 βt � RRp � dt +X0ptγ+ εpt

upt is urban population in pixel cell p at time tdt is a time feδp is a pixel feRRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

upt is urban population in pixel cell p at time t

dt is a time feδp is a pixel feRRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

upt is urban population in pixel cell p at time tdt is a time fe

δp is a pixel feRRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

upt is urban population in pixel cell p at time tdt is a time feδp is a pixel fe

RRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

upt is urban population in pixel cell p at time tdt is a time feδp is a pixel feRRp is our Roman road indicator (either a dummy or acontinuous variable)

Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

upt is urban population in pixel cell p at time tdt is a time feδp is a pixel feRRp is our Roman road indicator (either a dummy or acontinuous variable)Xpt is set of geographical controls interacted with timedummies (distance to: ocean, river, border, Rome; Easternempire dummy

Identi�cation issues

Measurement error in road variable?

More developed countries exert more archaeological e¤ort?Certain geographies more prone to road depreciation?

Eastern part of empire more developed than the Western, isthe relationship di¤erent in the two parts?

In�uence of pre-existing centers and colonies in Western part(Capua, Piacenza, etc)

More developed countries exert more archaeological e¤ort?

Certain geographies more prone to road depreciation?

Panel: Urban population 1200-1850

Table 2: Roads and urban population in 1200-1850(1) (2) (3)

Log Urban PopulationRR dummy RR cont RR c (no E.R)

RR*1300 1.13*** 0.46*** 0.46***RR*1400 0.60** 0.26* 0.25RR*1500 1.26*** 0.30* 0.36**RR*1600 1.29*** 0.39** 0.38*RR*1700 1.98*** 0.51*** 0.56***RR*1800 2.28*** 0.66*** 0.73***RR*1850 2.15*** 0.80*** 0.86***Controls, etc Yes Yes YesObs 4,832 3,024 2,728R2 0.34 0.39 0.38

Robust se. *** p<0.01, ** p<0.05, * p<0.1

Estimates from panel 1200-1850

Figure: The �gure shows the elasticity of urban population with respectto Roman Roads along the extensive and intensive margin, respectively,1300-1850. Notes: The �gures depicts the size of the estimates reportedin tables 3 and 4, column 8.

Econometric speci�cation: Contemporary analysis

log (ypc ) = δc + β � RRp +X0pγ+ εp

ypc is lights intensity or population density in pixel cell p incountry cδp is a country feRRp is our Roman road indicator (either a dummy or acontinuous logged variable)Xpt is set of controls

ypc is lights intensity or population density in pixel cell p incountry c

δp is a country feRRp is our Roman road indicator (either a dummy or acontinuous logged variable)Xpt is set of controls

ypc is lights intensity or population density in pixel cell p incountry cδp is a country fe

RRp is our Roman road indicator (either a dummy or acontinuous logged variable)Xpt is set of controls

ypc is lights intensity or population density in pixel cell p incountry cδp is a country feRRp is our Roman road indicator (either a dummy or acontinuous logged variable)

Xpt is set of controls

ypc is lights intensity or population density in pixel cell p incountry cδp is a country feRRp is our Roman road indicator (either a dummy or acontinuous logged variable)Xpt is set of controls

Lights intensity in 2012

Table 3: Roads and lights in 2012(1) (2) (3) (4) (5)

Log Lights in 2012RR dummy RR dummy RR cont RR cont RR cont

Roman road 0.60*** 0.14*** 0.20*** 0.11*** 0.07***(0.10) (0.04) (0.02) (0.03) 0.02

Log Area Y Y Y Y YAll controls N Y N N YCountry fe N Y N Y YObservations 972 933 485 485 469R2 0.18 0.60 0.19 0.58 0.65

*** p<0.01, ** p<0.05, * p<0.1

Population density in 2000

Table 4: Roads and population density(1) (2) (3) (4) (5)

Log Population in 2000RR dummy RR dummy RR cont RR cont RR cont

Roman road 1.26*** 0.48*** 0.21*** 0.16*** 0.09***(0.41) (0.15) (0.04) (0.05) 0.04

Log Area Y Y Y Y YAll controls N Y N N YCountry fe N Y N Y YObservations 972 933 485 485 469R2 0.47 0.70 0.41 0.61 0.69

*** p<0.01, ** p<0.05, * p<0.1

Intermediate channels

Modern roads are built on Roman roads?

Location of universities, a¤ecting the spread of knowledge(Bologna 1088; Paris, 1150; Salamanca, 1218; Naples, 1224;Toulouse, 1229; Montpellier, 1289; Florence, 1321)

Bishoprics and the organization of the Catholic Church(accumulation of wealth, power and human capital)

Universities and bishoprics

Concluding remarks

Our objective was to identify a long-run causal impact ofRoman roads on historical and contemporary levels ofdevelopment

Historical road intensity strongly predicts historical urbanpopulation levels and current levels of economic activity

Future work:

Explore intermediate channels: Modern roads are built onRoman roads?Universities and the Catholic church

Concluding remarks

Future work:

Concluding remarks

Future work:

Concluding remarks

Future work:

Explore intermediate channels: Modern roads are built onRoman roads?

Universities and the Catholic church

Concluding remarks

Future work:

roman roads to prosperity: the long&run impact of transport

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