Why Nations Fail

particularly unstable because of the concentration of power
in the hands of the emperor and his entourage. In a pattern
not too different from what happened in the Maya city-
states, infighting to take control of this powerful position
increased. Civil wars became a regular occurrence, even
before the chaotic fifth century, when the barbarians ruled
supreme. For example, Septimius Severus seized power
from Didius Julianus, who had made himself emperor after
the murder of Pertinax in 
AD
193. Severus, the third
emperor in the so-called Year of the Five Emperors, then
waged war against his rival claimants, the generals
Pescennius Niger and Clodius Albinus, who were finally
defeated i n 
AD
194 and 197, respectively. Severus
confiscated all the property of his losing opponents in the

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ensuing civil war. Though able rulers, such as Trajan (
AD
98
to 117), Hadrian, and Marcus Aurelius in the next century,
could stanch decline, they could not, or did not want to,
address the fundamental institutional problems. None of
these men proposed abandoning the empire or re-creating
effective political institutions along the lines of the Roman
Republic. Marcus Aurelius, for all his successes, was
followed by his son Commodus, who was more like
Caligula or Nero than his father.
The rising instability was evident from the layout and
location of towns and cities in the empire. By the third
century 
AD
every sizeable city in the empire had a defensive
wall. In many cases monuments were plundered for stone,
which was used in fortifications. In Gaul before the Romans
had arrived in 125 
BC
, it was usual to build settlements on
hilltops, since these were more easily defended. With the
initial arrival of Rome, settlements moved down to the
plains. In the third century, this trend was reversed.
Along with mounting political instability came changes in
society that moved economic institutions toward greater
extraction. Though citizenship was expanded to the extent
that by 
AD
212 nearly all the inhabitants of the empire were
citizens, this change went along with changes in status
between citizens. Any sense that there might have been of
equality before the law deteriorated. For example, by the
reign of Hadrian (
AD
117 to 138), there were clear
differences in the types of laws applied to different
categories of Roman citizen. Just as important, the role of
citizens was completely different from how it had been in
the days of the Roman Republic, when they were able to
exercise some power over political and economic
decisions through the assemblies in Rome.
Slavery remained a constant throughout Rome, though
there is some controversy over whether the fraction of
slaves in the population actually declined over the
centuries. Equally important, as the empire developed,
more and more agricultural workers were reduced to semi-
servile status and tied to the land. The status of these
servile 
“coloni”
is extensively discussed in legal documents
such as the 
Codex Theodosianus
and 
Codex Justinianus
,
and probably originated during the reign of Diocletian (
AD
284 to 305). The rights of landlords over the 
coloni
were

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progressively increased. The emperor Constantine in 332
allowed landlords to chain a 
colonus
whom they suspected
was trying to escape, and from 
AD
365, 
coloni
were not
allowed to sell their own property without their landlord’s
permission.
Just as we can use shipwrecks and the Greenland ice
cores to track the economic expansion of Rome during
earlier periods, we can use them also to trace its decline.
B y 
AD
500 the peak of 180 ships was reduced to 20. As
Rome declined, Mediterranean trade collapsed, and some
scholars have even argued that it did not return to its
Roman height until the nineteenth century. The Greenland
ice tells a similar story. The Romans used silver for coins,
and lead had many uses, including for pipes and tableware.
After peaking in the first century 
AD
, the deposits of lead,
silver, and copper in the ice cores declined.
The experience of economic growth during the Roman
Republic was impressive, as were other examples of
growth under extractive institutions, such as the Soviet
Union. But that growth was limited and was not sustained,
even when it is taken into account that it occurred under