ECON問題 10分

In Keynesian model, injection refers to those factors which make the flow of income rise while withdrawal refers to those factors which make the flow of income fall.
They will be equal only if the equilibrium is attained.
On the demand side, expenditures come from different sectors. E=C+I+G+X-M ,
On the supply side, income will be spent ,taxed or saved;Y=C+S+T,
As Y will change whenever E≠Y, Y will be at equilibrium when E=Y.
That means when Y=Ye, ( Ye stands for equilibrium income)
C+I+G+X-M = C+S+T,
I+G+X-M = S+T
hence I+G+X = S+T+M ; injection = withdrawal
Please note that it is not an identity, it is the equilibrium condition!

詳細的不記得了

Investment = Saving (你的人工減去 consumption 就是 saving,擺入銀行都算 investment)
如果是一個 balanced budget, 政府的收入(tax)等如支出(goverment expenditure)
如果是一個 balanced trade, 入口(import)等如出口(export)

如果三個條件都滿足,就會出現你所說的情況
但不一定是等如的....

個答案我也不確定喎!