Household Saving Behavior
The question
Households in the economy of Alta, expecting higher incomes in the future, increase current consumption and reduce the portion of income they save at each real interest rate. Assume firms' desired investment spending at each real interest rate is unchanged. Show the effect of this change in the loanable funds market. Show the effect on the Loanable Funds Market graph.
Drag a curve, or use the arrow buttons. Want the free-play version with every control? Open this graph in the sandbox.
Household Saving Behavior: the worked answer
On the Loanable Funds Market graph, Supply of loanable funds shifts left.
Why Supply of loanable funds shifts left
Household saving is the source of the supply of loanable funds. When households consume more and save a smaller portion of income at each real interest rate, fewer funds are made available to borrowers. The supply of loanable funds shifts to the left, while firms' demand for funds is unaffected because their desired investment at each interest rate has not changed.
What happens to the equilibrium
The equilibrium real interest rate rises and the equilibrium quantity of loanable funds decreases.
The mistake students make on this one
A frequent wrong answer is to shift the demand for loanable funds right because households are spending more, importing the logic of the product market where extra consumption raises demand. The demand curve here is borrowing to finance capital, and the stem holds firms' investment fixed; what actually changed is how much income households release to lenders.
On exam day
Find the sentence about saving out of income. Whatever happens to that flow happens to the supply of loanable funds, no matter which motive the stem gives for the change.
How this is graded
The checker reads every curve's position before and after your answer. You are marked correct only when Supply of loanable funds shifts left and every other curve on the Loanable Funds Market graph stays where it started — the same standard an AP reader applies to a drawn graph: the right shift, and nothing extra. There is no AI involved; the rubric is the geometry.
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