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).
From the uses perspective, national income (GDP) can be used for:
GDP = C + S + T
which says that GDP (income) ultimately comes back to households who consume (C), save (S) or pay taxes (T) with it once all the distributions are made.
Equating these two perspectives we get:
C + S + T = GDP = C + I + G + (X – M)
So after rearranging this equation we get the sectoral balances view of the national accounts:
(I – S) + (G – T) + (X – M) = 0
That is the three balances have to sum to zero. The sectoral balances derived are:
- The private domestic balance (I – S) – positive if in deficit, negative if in surplus.
- The Budget Deficit (G – T) – negative if in surplus, positive if in deficit.
- The Current Account balance (X – M) – positive if in surplus, negative if in deficit.
These balances are usually expressed as a per cent of GDP but that doesn’t alter the accounting rules that they sum to zero, it just means the balance to GDP ratios sum to zero.
A simplification is to add (I – S) + (X – M) and call it the non-government sector. Then you get the basic result that the government balance equals exactly $-for-$ (absolutely or as a per cent of GDP) the non-government balance (the sum of the private domestic and external balances).
This is a basic rule derived from the national accounts and has to apply at all times.
REF: Paj Holden
Whilst most of this was provided by Bill Mitchell we think it would be more appropriate for you to comment on this blog here at Modern Money.