I look at this through the lens of “sectoral financial balances”, an analytical framework learned from the work of the late Wynne Godley. The essential idea is that since income has to equal expenditure for the economy, as a whole, (which is the same things as saying that saving equals investment) so the sums of the difference between income and expenditures of each of the sectors of the economy must also be zero. These differences can also be described as “financial balances”. Thus, if a sector is spending less than its income it must be accumulating (net) claims on other sectors.
The crucial point is that, since sectoral balances must sum to zero, a rise in the deficit of one sector must be matched by an offsetting change in the others. It follows that if the fiscal deficit is increasing, the sum of the surpluses of the other sectors of the economy must be increasing in a precisely offsetting manner. Read more