An Aging Population
The question
The population of Aldemar has aged rapidly. A very large cohort has now reached retirement, stopped earning wages, and begun drawing down the wealth it built up over a working lifetime to cover living expenses. Assume firms' desired investment at each real interest rate is unchanged. Show the effect of this demographic change in Aldemar's 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.
An Aging Population: the worked answer
On the Loanable Funds Market graph, Supply of loanable funds shifts left.
Why Supply of loanable funds shifts left
The supply of loanable funds is national saving, the flow of funds households make available to borrowers. Retirees who spend down accumulated wealth are dissaving, and with a smaller share of the population still adding to savings out of wage income, fewer funds are offered to borrowers at every real interest rate, so the supply of loanable funds shifts to the left. Firms' desired investment is unchanged by assumption, so the demand for loanable funds stays put.
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
Students often shift demand left instead, reasoning that an older, smaller workforce means the economy produces and spends less, so firms need less financing. The stem holds firms' desired investment fixed at each interest rate, and retirees drawing down wealth changes who is lending, not who is borrowing.
On exam day
Demographics reach this graph through saving. Ask whether the group described is adding to the pool of funds or drawing it down, then move the lending side and leave borrowing alone.
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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