GDP map of the Roman Empire

[Imperial Dave]

http://brilliantmaps.com/roman-empire-gdp/

here's a really interesting talking point....GDP of the various provinces of the Roman Empire and how it compares (or not) to today

[Jim Webster]

http://brilliantmaps.com/roman-empire-gdp/

here's a really interesting talking point....GDP of the various provinces of the Roman Empire and how it compares (or not) to today

interesting

[Imperial Dave]

Not entirely convinced it can be compared like for like but very interesting nonetheless

[Patrick Waterson]

It is reminiscent of the Imperium Romanum II province values in Period I and II (early Empire).  Curiously, the site terms it a GDP per capita map as opposed to a GDP map - were the inhabitants of the higher-yielding provinces individually so much more productive than those elsewhere?

One may also consider that the skyrocketing value assigned to Italy presumably reflects the tendency of Rome to attract (or compel) resources from elsewhere rather than the Italians themselves being super-productive.

[Dangun]

It is reminiscent of the Imperium Romanum II province values in Period I and II (early Empire).  Curiously, the site terms it a GDP per capita map as opposed to a GDP map - were the inhabitants of the higher-yielding provinces individually so much more productive than those elsewhere?

Yes they were. We can tell that from quotes concerning tax revenues.

GDP is very difficult to estimate in pre-modern societies, making the population estimate look simple by comparison.
So I'd suggest a comparison between then and now is basically baseless/pointless.
But... as we've explored in another thread, a comparison of province to province is much more interesting.
I would like to know how they cam up with the GDP estimate.

To move closer to our area of interest, I think a province's GDP per mile of imperial border might be more interesting.
Sort of a what we get / what we lose kind of ratio.

[Imperial Dave]

Always going to be difficult in terms of like for like comparisons. As suggested in inter province one is of more use. What about outside the empire...how do we attempt to validate that

[Patrick Waterson]

To move closer to our area of interest, I think a province's GDP per mile of imperial border might be more interesting.

The first and most obvious observation is that there is a massive difference between East and West.  In the east itself, Commagene and Syria have the same GDP categorisation as Asia and Galatia but very different 'border miles'.  Incidentally, should one count desert borders (important for Libya, Africa etc.) and if so how should these be weighted compared to borders adjoining Mesopotamia and along the Rhine and Danube?

The next observation is that in the west there seems to be a clear correlation between the GDP of a province and the length of time it has spent in the Empire.  This is worth bearing in mind when wondering about the cost of maintaining legions on borders.

Some provinces have no imperial border, and hence would have infinite GDP by comparison with the remainder.  These, of course, were usually the provinces without legions.

To be meaningful, we really need to look at the Empire as a whole, otherwise there is a danger of seeing it through the eyes of a consultant advising the Romans to concentrate on their economic core competences and letting the frontier provinces go as uneconomic, which would leave several populations of unreformed barbarians whose population had grown, who were familiar with Roman organisation and weaponry and who may have felt they wished to settle some old scores.  (Remember Civilis! )

[Dangun]

The next observation is that in the west there seems to be a clear correlation between the GDP of a province and the length of time it has spent in the Empire.  This is worth bearing in mind when wondering about the cost of maintaining legions on borders.

This makes some economic sense - cumulative investment e.g. roads, aqueducts, ports etc should increase GDP. It is probably an incomplete explanation, but does make some sense.

To be meaningful, we really need to look at the Empire as a whole, otherwise there is a danger of seeing it through the eyes of a consultant advising the Romans to concentrate on their economic core competences and letting the frontier provinces go as uneconomic

I don't see why this is a danger, when it may simply be the case that some provinces are uneconomic. Such a question seems pretty simple to answer too.

We can complicate the analysis by saying, its not that simple, for example, we might want to argue that we have to hold all this uneconomic German territory to keep X, and Y economic territory. But in some cases it is pretty simple. For example, was Britain an economic positive or negative? Was Mesopotamia an economic positive or negative? In these cases, there is certainly an answer, we might not have the answer, and the range of possibilities is attractively binary.

[Patrick Waterson]

Then, of course, we have places which are an economic negative but a security positive, like Germania Inferior and Superior.  Interestingly, the neither-one-thing-nor-the-other provinces (Agri Decumates and Dacia) were the first to be abandoned, suggesting the Romans did their own cost-benefit analyses, admittedly when under stress.

In the east, the provinces seem to have been worthwhile economically but subject to competition from whoever ruled the Persian territories at the time.  The result was much money spent not only acquiring and retaining provinces but also, as Rome increasingly took over direct administration as opposed to letting local princes do it, fortifying and otherwise securing the borders.  There was a good reason for this: when the defences failed (as in the mid-3rd century AD) the Sassanids penetrated deep into the economic heartland of the east (notably Syria) and caused great loss and damage.

Part of the imperial defence system was, where possible, to secure the chap beyond the border as a client king.  He then kept at arms length his immediate neighbours, which in turn discouraged him from becomong too interested in testing out the Empire's defences.  When this system broke down, it became necessary to establish limitanei - a border force which dealt with small parties of barbarians and provided a 'trip-wire' warning system for larger incursions - this in addition to the legionary armies at various stations.

By the time of Diocletian's successors, the majority of the good troops were no longer located in the frontier provinces, but held in palatini armies around major cities in the wealthier provinces, to be committed when required.  This of course spread the maintenance load (although it all came form the Imperial treasury in the end) and in addition adjusts the costing for various provinces, because no longer can one notionally assign the costs of defending the Empire to the frontier provinces.

We can complicate the analysis by saying, its not that simple, for example, we might want to argue that we have to hold all this uneconomic German territory to keep X, and Y economic territory. But in some cases it is pretty simple. For example, was Britain an economic positive or negative? Was Mesopotamia an economic positive or negative? In these cases, there is certainly an answer, we might not have the answer, and the range of possibilities is attractively binary.

Britain was an economic positive , probably from the 2nd century AD, certainly in the 3rd when under Carausius it left the Empire, flourished and was definitely missed until reclaimed by Constantius Chlorus.

Mesopotamia, when held, would have been an economic positive (which is why Parthians, Persians etc, always strove to hold it), but the problem was that from the Roman point of view it was a political negative: once conquered by Trajan, it comprehensively revolted, which led Hadrian to withdraw from it entirely.

[Dangun]

Britain was an economic positive , probably from the 2nd century AD, certainly in the 3rd when under Carausius it left the Empire, flourished and was definitely missed until reclaimed by Constantius Chlorus.

Mesopotamia, when held, would have been an economic positive (which is why Parthians, Persians etc, always strove to hold it), but the problem was that from the Roman point of view it was a political negative: once conquered by Trajan, it comprehensively revolted, which led Hadrian to withdraw from it entirely.

I may be misunderstanding your intention, but it sounds as though you are suggesting - particularly in regards to Mesopotamia - that you are suggesting that any territory is economically positive... if only it was peaceful. But that's the problem with province Mesopotamia, you cannot expect it to be peaceful and productive because you will be constantly at war with angry Persians and Parthians throwing resources away on something you can't hold.

We can tell that there were a lot of uneconomic / economically negative provinces simply from how close to balanced the budget was, and with Italy and Egypt so productive there are economic sinks to be identified.

[Patrick Waterson]

I may be misunderstanding your intention, but it sounds as though you are suggesting - particularly in regards to Mesopotamia - that you are suggesting that any territory is economically positive... if only it was peaceful.

Almost any territory - they did start out self-sustaining before the Romans acquired them.  Conversely, the composite Agri Decumates were a frontier region not based on a specific local population and culture, an artificial entity populated by settlers, and seemingly not worth the effort of recovery after Gallienus' reign.  Ultimately, the effort of recovery seems to have been the principal criterion for retention until Dacia was knowingly and deliberately abandoned c.275 BC; by this time it had been combed by repeated barbarian invasions and Aurelian seems to have considered was not worth the trouble of rebuilding when its surviving personnel would be more useful fleshing out similarly-depleted Moesia.  It is nevertheless worth noting how much effort the Roman put into making Dacia 'profitable'.

But that's the problem with province Mesopotamia, you cannot expect it to be peaceful and productive because you will be constantly at war with angry Persians and Parthians throwing resources away on something you can't hold.

But this will be true of whatever region is adjacent to the Parthian (or Sassanid) Empire.  The specific problem with Mesopotamia was not proximity to a (recently-defeated) foe, but the fact that it rose in rebellion so comprehensively that Hadrian, who later was prepared to commit ten legions and several years to suppressing the Bar-Kochba revolt in Judaea, considered it a lost cause and withdrew.

We can tell that there were a lot of uneconomic / economically negative provinces simply from how close to balanced the budget was, and with Italy and Egypt so productive there are economic sinks to be identified.

Perhaps not so much provinces as processes: Imperial tax collection left much to be desired, as shown when Julian overhauled the administration of Gaul and had everything running for a capitation tax of 7 gold pieces as against the previous 25.  This was during a time of intensive campaigning against the German tribes, who had been invading and despoiling the province, so it was hardly at peak performance.

Where my main reservations lie is in a purely economic or financial analysis: this tends to ignore vital considerations (political, both with regard to threats on the borders and the internal stability of provinces) and overlooks the possibility of internal improvement making the system more effective.

We should perhaps also note that when the Empire was expanding in the 1st century BC/early 1st century AD, some territories, notably Germania and Illyria (and even areas of Hispania) required much force to subdue, such that the province was definitely a financial loss.  However subduing these provinces was essential for the integration of the Empire (Illyria so that east-west travel need not be wholly by sea, for example) and the only province of the three not ultimately subdued was Germania.  Why?  Because it launched a successful rebellion and subsequently avoided decisive military defeat.

One serious problem with attempting to evaluate each province as a 'defence liability' is that the legions have to be paid wherever they are, and another very serious consideration is that they are not the only item dealt with by the Imperial exchequer.  Buildings, entertainments and prestige projects generally (plus the corn distribution for the citizenry of Rome) all featured as expense items, and under some early emperors expenditures got out of hand.  It is noticeable how the exchequer filled up under Tiberius, was emptied by Caligula, restocked by Claudius (despite the supposed expenses of campaigning in Britannia) and squandered by Nero, Otho and Vitellius before being refilled by Vespasian.  Personalities mattered, and converted the underlying economics into an easy positive balance or a dead loss.  Yet the fact that sensible rulers were well able to build up a surplus shows that the underlying economics were sound, whether or not some individual provinces might be considered 'loss-makers', which is itself a questionable assumption given the Roman determination to make provinces pay.

This goes back to the old Biblical question of how you set a level of tribute (taxation is basically tribute with a different middleman).  Back in Biblical days, most civilisations seem to have had extensive bureaucracies which assessed each man individually.  Rome, once the Empire became settled, seems to have subcontracted the procedure but the essential approach was the same.  In the later Empire, there seems to have been a 'collective entity approach' in that taxpayers were grouped into units, and each unit would pay a level of tax determined by the 'needs' of the Empire - this is the assessment Julian so dramatically reduced in Gaul during his rule there.  The point here is that if a province was deemed uneconomic, its yield could be raised to the level of being economic - obviously only so far before it became ruined, but there was an element of flexibility there.  And this flexibility need not have a direct relationship to 'per capita GDP': the driving force was a perceived need for additional revenue.

And this concludes the lecture ...

[Duncan Head]

It is nevertheless worth noting how much effort the Roman put into making Dacia 'profitable'.

Wikipedia - https://en.wikipedia.org/wiki/Roman_Dacia#Economy - and I have made no effort to check out its sources - suggests that "Evidence points to the closure of the gold mines around the year 215 AD". Is the story of Dacia perhaps simply that for the first century or so it was very profitable, and worth the considerable military investment to secure it, but ceased to be so when the gold ran out?

[Imperial Dave]

Always going to be a driver....precious metals and other important commodities. One wonders why Britain remained high on the empires agenda when it wasn't all that profitable...ie the high level of maintenance required

[Mark G]

Interesting though Duncan.

I would have thought defending the Danube was the reason, but exhausting the mines may better fit the chronology .

Can we test it?

And were the romans much good at finding new mines?

[Patrick Waterson]

Is the story of Dacia perhaps simply that for the first century or so it was very profitable, and worth the considerable military investment to secure it, but ceased to be so when the gold ran out?

Possibly, although it also had salt, iron, silver, and copper mines, various useful building stones and several flourishing manufacturies.  While the gold running out doubtless made it less of a - erm - gold mine, there seems to have still been plenty of economic life there.  The mines ran out c.AD 215; the Romans ran out c.AD 275.  Sixty goldless years seems a long time to hold a supposedly impecunious province.

What does seem to have finished it off was the depopulation caused by a combination of plague and repeated barbarian invasions, which caused Aurelian to pull the plug.

The province of Dacia, which Trajan had formed beyond the Danube, he gave up, despairing, after all Illyricum and Moesia had been depopulated, of being able to retain it. The Roman citizens, removed from the town and lands of Dacia, he settled in the interior of Moesia, calling that Dacia which now divides the two Moesiae, and which is on the right hand of the Danube as it runs to the sea, whereas Dacia was previously on the left. — Eutropius IX.15

One wonders why Britain remained high on the empires agenda when it wasn't all that profitable...ie the high level of maintenance required

It was nevertheless considered worth reconquering, and, while the Empire remained intact, retaining.  It seems to have had virtues over and above a simple positive cash balance: Julian brought in significant quantities of grain from Britannia to restock towns along and near the Rhine, which suggests Britain was an important grain-producing area in the late Empire.  Also, the Bordeaux wine merchants needed someone who would pay for their produce ...