Only one of the following propositions is possible for a nation with an external deficit over any given period (with all balances expressed as a per cent of GDP)
Answer: A public surplus of equal size to the external deficit, with the private domestic sector dis-saving overall.
The best answer is the second option - "An external deficit accompanied by a public surplus of equal size and the private domestic sector spending dis-saving overall".
This is a question about the sectoral balances - the government fiscal balance, the external balance and the private domestic balance - that have to always add to zero because they are derived as an accounting identity from the national accounts.
To refresh your memory the sectoral balances are derived as follows. The basic income-expenditure model in macroeconomics can be viewed in (at least) two ways: (a) from the perspective of the sources of spending; and (b) from the perspective of the uses of the income produced. Bringing these two perspectives (of the same thing) together generates the sectoral balances.
From the sources perspective we write:
GDP = C + I + G + (X - M)
which says that total national income (GDP) is the sum of total final consumption spending (C), total private investment (I), total government spending (G) and net exports (X - M).
Expression (1) tells us that total income in the economy per period will be exactly equal to total spending from all sources of expenditure.
We also have to acknowledge that financial balances of the sectors are impacted by net government taxes (T) which includes all taxes and transfer and interest payments (the latter are not counted independently in the expenditure Expression (1)).
Further, as noted above the trade account is only one aspect of the financial flows between the domestic economy and the external sector. we have to include net external income flows (FNI).
Adding in the net external income flows (FNI) to Expression (2) for GDP we get the familiar gross national product or gross national income measure (GNP):
(2) GNP = C + I + G + (X - M) + FNI
To render this approach into the sectoral balances form, we subtract total taxes and transfers (T) from both sides of Expression (3) to get:
(3) GNP - T = C + I + G + (X - M) + FNI - T
Now we can collect the terms by arranging them according to the three sectoral balances:
(4) (GNP - C - T) - I = (G - T) + (X - M + FNI)
The the terms in Expression (4) are relatively easy to understand now.
The term (GNP - C - T) represents total income less the amount consumed less the amount paid to government in taxes (taking into account transfers coming the other way). In other words, it represents private domestic saving.
The left-hand side of Equation (4), (GNP - C - T) - I, thus is the overall saving of the private domestic sector, which is distinct from total household saving denoted by the term (GNP - C - T).
In other words, the left-hand side of Equation (4) is the private domestic financial balance and if it is positive then the sector is spending less than its total income and if it is negative the sector is spending more than it total income.
The term (G - T) is the government financial balance and is in deficit if government spending (G) is greater than government tax revenue minus transfers (T), and in surplus if the balance is negative.
Finally, the other right-hand side term (X - M + FNI) is the external financial balance, commonly known as the current account balance (CAB). It is in surplus if positive and deficit if negative.
In English we could say that:
The private financial balance equals the sum of the government financial balance plus the current account balance.
We can re-write Expression (6) in this way to get the sectoral balances equation:
(5) (S - I) = (G - T) + CAB
which is interpreted as meaning that government sector deficits (G - T > 0) and current account surpluses (CAB > 0) generate national income and net financial assets for the private domestic sector.
Conversely, government surpluses (G - T < 0) and current account deficits (CAB < 0) reduce national income and undermine the capacity of the private domestic sector to add financial assets.
Expression (5) can also be written as:
(6) [(S - I) - CAB] = (G - T)
where the term on the left-hand side [(S - I) - CAB] is the non-government sector financial balance and is of equal and opposite sign to the government financial balance.
This is the familiar MMT statement that a government sector deficit (surplus) is equal dollar-for-dollar to the non-government sector surplus (deficit).
The sectoral balances equation says that total private savings (S) minus private investment (I) has to equal the public deficit (spending, G minus taxes, T) plus net exports (exports (X) minus imports (M)) plus net income transfers.
All these relationships (equations) hold as a matter of accounting and not matters of opinion.
The following Table helps us answer the question.
| Sectoral Balance | Interpretation of Result | Case A | Case B | Case C |
| External Balance (X - M) | Deficit is negative | -2 | -2 | -2 |
| Fiscal Balance (G - T) | Deficit is positive | -1 | -2 | -3 |
| Private Domestic Balance (S - I) | Deficit is negative | -3 | -4 | -5 |
We have an external deficit of 2 per cent of GDP in each of the three cases.
In Case A, we have a fiscal surplus of 1 per cent of GDP (so smaller than the external deficit), and the private domestic sector is in deficit of 3 per cent of GDP - that is, dis-saving overall.
Remember this is not referring to household saving. It is the overall private domestic sector balance we are discussing here. The sector can be in deficit even if the households are saving.
In Case B, we now have a fiscal surplus equivalent to the external deficit and the private domestic sector is dis-saving ((spending more than they are earning and increasing its indebtedness).
In Case C, with the fiscal surplus rising above the external deficit, the private domestic sector deficit increases further to 5 per cent of GDP.
So the answer to the question is clearly false.
With an external deficit and a fiscal surplus of any magnitude, the private domestic sector will run deficits.
What is the economic rationale for this conclusion?
If the nation is running an external deficit it means that the contribution to aggregate demand from the external sector is negative - that is net drain of spending - dragging output down.
The external deficit also means that foreigners are increasing financial claims denominated in the local currency. Given that exports represent a real costs and imports a real benefit, the motivation for a nation running a net exports surplus (the exporting nation in this case) must be to accumulate financial claims (assets) denominated in the currency of the nation running the external deficit.
A fiscal surplus also means the government is spending less than it is "earning" and that puts a drag on aggregate demand and constrains the ability of the economy to grow.
In these circumstances, for income to be stable, the private domestic sector has to spend more than they earn.
You can see this by going back to the aggregate demand relations above. For those who like simple algebra we can manipulate the aggregate demand model to see this more clearly.
Y = GDP = C + I + G + (X - M)
which says that the total national income (Y or GDP) is the sum of total final consumption spending (C), total private investment (I), total government spending (G) and net exports (X - M).
So if the G is spending less than it is "earning" and the external sector is adding less income (X) than it is absorbing spending (M), then the other spending components must be greater than total income
The following blog posts may be of further interest to you: