This document provides an abstract for a PhD thesis on the economy of the Roman Empire from the 1st to 3rd centuries AD. The thesis will take a quantitative approach, analyzing numbers related to agricultural productivity, urban population size, life expectancy, and coinage silver content. It will examine the structure of the Roman economy in terms of the separation of towns and countryside. It will compare Roman economic performance to other historical economies based on factors like productivity, trade infrastructure, and knowledge. The thesis aims to assess how well the Roman economy performed relative to its technology and to identify institutions that contributed to or hindered economic achievement.

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The Secrets of Economic Success and the Causes of
Failure
The Case of Imperial Rome
George P. M. Maher
King's College London
2015
Thesis submitted for the degree of Doctor of Philosophy

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To my parents

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ABSTRACT
The subject of this thesis is the economy of the Roman Empire from the beginning of the first
through to the end of the third centuries AD. The approach taken is partly quantitative and
draws on detailed quantitative research undertaken by scholars across a wide area. I
concentrate the analysis on those few numbers which are likely to have the richest
explanatory power and I consider the relationships between those numbers. The numbers
analysed include the average amount of grain produced on a hectare of land, the size of the
urban population, the average life expectancy and the silver content of the coinage. The
approach also considers the institutions of imperial Rome, to the extent that they are relevant
to economic achievement.
I consider the structure of the economy of the Roman Empire in terms of the separation of
town and country, the agglomeration of individuals in the towns and the connections between
those towns. I map out the development of the economy over time with a discussion of the
creation and destruction of its currency.
I compare the performance of the economy of the Roman Empire with that of other
economies by considering rural and urban productivity, trading activity, the infrastructure
that supported trade and the knowledge base used in the production of goods and services.
The question that this thesis addresses is the following: How well did the economy of
imperial Rome preform in terms of the quantity and quality of goods and services produced
relative to the technology available and in comparison with medieval and later economies and
which institutions contributed to or hindered economic achievement?
I believe that the achievements of the Roman Empire in this period provide important lessons
as to what is possible in economies generally and where some of the risks to economic
success lie.

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TABLE OF CONTENTS
1. Introduction 11
1.1. Purpose 11
1.2. Economic achievement defined 11
1.3. Previous approaches 11
1.4. My approach 13
1.4.1. Numbers 14
1.4.2. Relationships between numbers 16
1.5. The experiment 16
2. The agricultural sector and comparisons to other economies 18
2.1. Introduction 18
2.2. Seed productivity 19
2.2.1. Analysis of Roman seed productivity 19
2.2.2. Comparisons to other economies 28
2.3. Consumption 36
2.4. Labour structures 39
2.5. Conclusions 46
3. Levels of urbanisation and economic output 48
3.1. Introduction 48
3.2. The debate 48
3.3. Urban structures 49
3.4. The relationship between agricultural surplus and urbanisation 54
3.5. The relationship between the transport system and the size of towns 59
3.6. The relationship between urbanisation and total output 63
3.7. Productivity 67
3.8. Conclusions 76

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4. The extent of trade and how it changed over time 79
4.1. Introduction 79
4.2. Previous approaches to trade in the economy of the Roman empire 79
4.3. Trade and Theory 82
4.3.1. Why goods are moved 82
4.3.2. Risks and costs which are a deterrent to trade 84
4.3.3. Intermediation 85
4.3.4. The prerequisites for trade 85
4.3.5. Scale of profits 86
4.4. What goods were moved and why 88
4.4.1. Wheat 88
4.4.2. Wine 89
4.4.3. Overall patterns 90
4.5. Risks and costs that restricted trade 90
4.5.1. Shipwreck and piracy 90
4.5.2. Inflation 92
4.5.3. Commercial risks 93
4.5.4. Costs 93
4.6. Intermediation 95
4.6.1. The Ship-Owner 95
4.6.2. Merchants 96
4.6.3. Trading Structures 98
4.7. Prerequisites 101
4.7.1. Information flow 101
4.7.2. State 101
4.7.3. Money 102
4.7.4. Port Structure 102
4.8. Conclusions 107

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5. The expectation of life as a measure of economic progress 109
5.1. Introduction 109
5.2. The debate 109
5.3. The parameter P 111
5.4. Comparators and their implications 118
5.5. Relevant data and its interpretation 122
5.5.1. Inscription data 122
5.5.2. Ulpian’s evidence 125
5.5.3. Data from Roman Britain 126
5.5.4. The Egyptian data 128
5.6. Applying P to population growth 130
5.7. Conclusions 131
6. Productive knowledge and the potential for growth 133
6.1. Introduction 133
6.2. The debate 133
6.3. Knowledge, labour and growth 135
6.4. Financial knowledge 138
6.5. Engineering knowledge 144
6.5.1. Tacit knowledge 145
6.5.2. Infrastructure development 146
6.6. Agricultural knowledge 149
6.7. Conclusions 153
7. The money systemand its weaknesses 154
7.1. Introduction 154
7.2. Monetisation 154
7.3. The dynamics of the metallic currency 156
7.4. Relationship between the silver content of the denarius and inflation 162
7.5. Money supply – further features of this money system 163
7.5.1. State money creation 164
7.5.2. Private money creation 170
7.6. Inflation – the facts and the contributory factors 171
7.7. Conclusions 180

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8. The systemof state finances and fiscal incompetence 181
8.1. Introduction 181
8.2. The debate 182
8.3. Funding structures and flows 182
8.3.1. The continuing revenues and their importance 183
8.3.2. Other revenues 188
8.4. Capital expenditure 188
8.5. Current expenditure 191
8.5.1. Army manpower 192
8.5.2. Army pay accounts 193
8.5.3. Pay rates 195
8.6. State accounts 198
8.7. Conclusion 201
9. Conclusions 203
9.1. Introduction 203
9.2. Creation of the money system 203
9.3. Separation, agglomeration and connection 205
9.4. Destruction of the money system 208
9.5. The experiment 210
10. Appendices 212
11. Bibliography 221

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LIST OF FIGURES
2.1 History of English grain yields 33
2.2 History of European grain yields 34
3.1 Modern comparison of income and urbanisation levels 65
3.2 Total output as a multiple of rural output 66
4.1 Schematic illustration of the effect of profit retention on trade 87
5.1 Relationship between P and expectation of life: Model West 113
5.2 Relationship between P and expectation of life: All tables 114
5.3 Fit of British peerage data and English life tables 115
5.3 Relationship between P and expectation of life: British peerage 117
6.1 Modern wheat more productive than ancient wheat 151
7.1 Debasement of the coinage 167
7.2 State wheat prices 175
7.3 Private wheat prices 176
7.4 Private wine prices 177
7.5 Price of donkeys 178
7.6 Military pay 179
8.1 Schematic of current account revenue from Tribute 186
8.2 Illustration of variations in capital expenditure over time 196

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LIST OF TABLES
2.1 Summary of grain yields 26
2.2 The economic map 30
2.3 Example structure of agricultural unit 40
3.1 Distribution of town sizes 51
3.2 Illustration of structural changes in the English urban landscape 53
3.3 Relationship between the rural landscape and urbanisation 57
3.4 Relationship between land locked town size and hinterland radius 61
3.5 Comparison of land and sea supply 63
3.6 List of occupations 74
3.7 Relative earnings of different occupations 75
4.1 Shipwreck data 91
4.2 Freight charges for wheat 94
4.3 Change in processing capacity of principal ports around Rome 105
5.1 Illustration of the variety of mortality experiences 120
5.2 Illustration of a technique to estimate life expectancy 124
5.3 Example of the use of cemetery data 127
5.4 Difficulty of fitting Egyptian census data 129
5.5 Further difficulty of fitting Egyptian data 129
5.6 Relationship between births and intergenerational growth rates 130
7.1 Illustration of arbitrage opportunities 159
8.1 Summary of Capital Expenditure 190
8.2 Variations in army manpower over time 192
8.3 Example of soldiers pay accounts 193
8.4 Basic pay rates 196
8.5 Calculation of total cost of the army 199
8.6 Summary of scholarly estimates of total army costs 200
8.7 Schematic of State Current Account 200

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ACKNOWLEDGEMENTS
I am grateful to Professor Dominic Rathbone for supervising this thesis, for his continuing
encouragement, patience and helpfulness and especially for making this project so fascinating
and enjoyable.
I would also like to acknowledge the help I received from Dr Christy Constantalopoulou, Dr
Serafina Cuomo and Professor Catherine Edwards of Birkbeck who supervised my BA and
MA essays and dissertation and especially the discussions I had with Dr Cuomo on
knowledge and the economy.
Dr Andrew Hinde answered several emails and helped in my understanding of the history of
British demography. The late Professor John Crook introduced me to Ulpian’s valuation
functions and kindly sent me some relevant passages from the Digest. Dr Kris Lockyear gave
me useful background on Roman money and both Professor Henrik Mouritsen and Dr John
Pearce commented on the early draft of my chapter on agriculture. In addition I had a number
of conversations with Dr Pearce on grain productivity and on mortality. I had discussions
with Dr Alexandra Sapoznik on medieval and early modern grain productivity and my fellow
student Federico Ugolini and I discussed Roman port structures.
I had the benefit of insights into grain productivity from Patrick Mulcahy, a UK agronomist.
Phil Skelton and Peter Seymour, both of ACE Insurance, gave me useful context on modern
marine transportation. Adrian Gallup of the Government Actuary’s Department provided
helpful data extracted from the English Life Tables. Michael Townsend of the Institute of
Historical Research helped me by identifying sources for population estimates of English
towns. James McCormack, Sean McCormack and Martina Maher helped with the input of the
over 1,500 data points on Slicher van Bath wheat yields. Helen Maher, Andy Staudt and
Daniel Marx helped in the construction of some of the graphs and taught me how to make
them on my own. Julian Leigh and Chris Waites read a later and an early version of the text
respectively.
Finally I am very grateful for the support and continuing encouragement I received from
Anne-Marie Harvey, Mitesh Rajput and Dr William Loschert.