GDP map of the Roman Empire

[Dangun]

Almost any territory - they did start out self-sustaining before the Romans acquired them.

This is a good point and always worth remembering. 

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.

Agreed. Financial factors are never very good at proximate explanations, but its a very powerful tidal factor.

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

This is an interesting question and I can't recall a lot of Roman literature that talks about it. Maybe its like a Falkland-Islands-Affect - once its Roman, as a matter of principle you stubbornly resist giving it up, irregardless of the financial impact? Politically too, no one wants to be remembered as the leader who gave up said territory...

http://www.businessinsider.com/falkland-islands-cost-2012-2 suggests the cost of defending the Falklands' is about US$35,000 per inhabitant. Completely uneconomic. But possibly a necessary part of defending Greater London?? 

[Imperial Dave]

I do suspect that this is a lot to do with it to be fair. What was the parallel with other territories that the Romans did give up like Germans inferior and parts of Dacia?

[Patrick Waterson]

What was the parallel with other territories that the Romans did give up like Germans inferior and parts of Dacia?

The Romans did not give up Germania Inferior until after AD 408, and even then hung on to it indirectly by letting Franks settle there and keeping them as allies (most of the time).  What they gave up was the Agri Decumates, a settlement frontier zone between the Germanias and Rhaetia, and they did so only in the context of the Crisis of the Third Century, when widespread barbarian invasions, plague and Gallienus practically destroyed the Empire (Aurelian pulled it back together c.AD 272-274).  With the Empire back in hand, Aurelian let go both Dacia and Agri Decumates, which were:
1) Rome's most recent acquisitions
2) More exposed than any other provinces
3) Seriously depopulated (along with the rest of the Empire).

Somewhere in this combination of factors is probably the common reason for abandonment.  The Empire had lost something like half its population, and what there was needed to be used effectively.  Aurelian seems to have pulled the plug on the basis of population requirements as much as anything else; lack of sufficient people meant that something had to go, and these most exposed provinces drew the short straw.  My best guess is he decided he could afford to dispense with these but could not afford to abandon anything else.

Earlier on, Hadrian had rationalised Trajan's Dacia by granting the plains area to the Rhoxolani, in effect trading a wide extent of grass for a useful client state.  This meant that the U-shaped gap in the frontier was not a problem as it was inhabited by friendlies.  Naturally, a century later, when no longer inhabited by friendlies, it did become a problem, but this arose from failure/inability to adapt to a changed situation.

[Imperial Dave]

if manpower and population was an issue for relinquished areas....why was Britain kept...especially since it was a proverbial pain in terms of breakaway emperors

[Dangun]

Pieces of the middle east also periodically fell off.

2) More exposed than any other provinces
3) Seriously depopulated (along with the rest of the Empire).

I'd note that 2 and 3 are quite closely related to costs and revenues. 

[Patrick Waterson]

if manpower and population was an issue for relinquished areas....why was Britain kept...especially since it was a proverbial pain in terms of breakaway emperors

Precisely because it was populous enough to support breakaway emperors ...

Pieces of the middle east also periodically fell off.

Notably Palmyra, and again notably in the 3rd century crisis.  This too was regained by Aurelian, although in regaining Palmyra he destroyed its prosperity so it became more of a geographical footnote. 

2) More exposed than any other provinces
3) Seriously depopulated (along with the rest of the Empire).

I'd note that 2 and 3 are quite closely related to costs and revenues. 

I give you that.

They are also related to the ability to maintain a coherent economy and infrastructure, and this rather than any idea of a province paying its way or otherwise seems to have been Aurelian's criterion for abandonment.  We are after all talking about not a business but a government organisation.

[Jim Webster]

We are after all talking about not a business but a government organisation.

In this period, given their grasp of economic theory, would there be that much difference? There are times when you feel the Empire was run pretty much as you'd run a large landed estate, which is what many of the Emperors and their advisers effectively did for a living anyway 

[Patrick Waterson]

We are after all talking about not a business but a government organisation.

In this period, given their grasp of economic theory, would there be that much difference? There are times when you feel the Empire was run pretty much as you'd run a large landed estate, which is what many of the Emperors and their advisers effectively did for a living anyway 

And land was seen as the one asset with enduring value.  My thought was mainly about contrast with modern cost/benefit business analysis and accounting methods; as you rightly indicate, the Romans would be very unlikely to think the modern way.  Their idea of empire management would be less about disposal of loss-making assets and more about sending the tax gatherers out again to make up any shortfall.

[Erpingham]

It's a discussion we have had before, but as you say, it is dangerous to back-project the methods of modern capitalism onto ancient empires.  I would suggest that the Empire became the natural order of things and maintaining it was the Roman way.  Once somewhere had been added to the Empire, it was the Emperor's duty to maintain it in the Empire.  Ground was ceded only with great reluctance and not based on a set of Excel spreadsheets.

[Imperial Dave]

It's a discussion we have had before, but as you say, it is dangerous to back-project the methods of modern capitalism onto ancient empires.  I would suggest that the Empire became the natural order of things and maintaining it was the Roman way.  Once somewhere had been added to the Empire, it was the Emperor's duty to maintain it in the Empire.  Ground was ceded only with great reluctance and not based on a set of Excel spreadsheets.

so how does the likes of Hadrian fit in ie in terms of trying to define and 'fix' the outer markers of the empire....would GDP/wealth accrual come into the decision making process? 

[Jim Webster]

It's a discussion we have had before, but as you say, it is dangerous to back-project the methods of modern capitalism onto ancient empires.  I would suggest that the Empire became the natural order of things and maintaining it was the Roman way.  Once somewhere had been added to the Empire, it was the Emperor's duty to maintain it in the Empire.  Ground was ceded only with great reluctance and not based on a set of Excel spreadsheets.

so how does the likes of Hadrian fit in ie in terms of trying to define and 'fix' the outer markers of the empire....would GDP/wealth accrual come into the decision making process?

I suspect that it would be a mix of factors. The line of the frontier could be decided by geography (rivers are good, you know where they are, also they make excellent supply lines for getting bulk supplies to frontier garrisons stationed along them.)

[Erpingham]

To be clear, I don't think there were no cost/benefit calculations.  Just that financial considerations were not the sole element.  I also doubt whether per capita GDP was the financial factor at the top of everyone's minds.  Sustaining the elite that ran the Empire was probably a more active concern.

[RichT]

I can't speak for Romans, but to go off on a tangent, for Hellenistic kings it was a key part of royal ideology that a king should maintain and ideally add to the territories bequeathed to him by his predecessor. So once a territory was 'in', for whatever reason (and claiming territories 'won by the spear' was another key part of royal ideology), there would be a strong onus on subsequent kings to keep it in. No doubt if a territory turned out to pay lousy taxes, be full of rebellious subject, or require ruinous expense to defend, these rules could suddenly be found to be more like guidelines, but the shape of a Hellenistic kingdom wouldn't be determined primarily by considerations of cost/benefit analysis, GDP etc.

[Jim Webster]

I can't speak for Romans, but to go off on a tangent, for Hellenistic kings it was a key part of royal ideology that a king should maintain and ideally add to the territories bequeathed to him by his predecessor. So once a territory was 'in', for whatever reason (and claiming territories 'won by the spear' was another key part of royal ideology), there would be a strong onus on subsequent kings to keep it in. No doubt if a territory turned out to pay lousy taxes, be full of rebellious subject, or require ruinous expense to defend, these rules could suddenly be found to be more like guidelines, but the shape of a Hellenistic kingdom wouldn't be determined primarily by considerations of cost/benefit analysis, GDP etc.

I think the Hellenistic kingdoms, certainly the Seleucids, are a good example in that there were degrees of 'in'.
Some places would be autonomous but make regular generous gifts and allow their foreign policy to be guided by the King, whereas other places would have garrisons, pay tribute and obey orders.
Then you'd have tribal people within the Empire who might pay a nominal tribute, receive gifts to help them through bad winters and discourage them from having to raid, and would supply troops when asked and probably recruits even in peacetime
Areas could move between these various degrees but would still be 'in'

[Imperial Dave]

so in the Hellenistic world, a mixture of prestige, money opportunities and a flexible approach to the 'arrangements' used on a local level. In the Roman world more a case of pride/prestige and a solidification of 'this bit is mine'?