Syracuse University
Arlene's intertemporal budget constraint has the usual form:
I0 + I1/(1+r) = C0 + C1/(1+r)
The left side, or present value of her income, is straightforward to calculate:
I0 + I1/(1+r) = $100k + $30k/1.1 = $127.3k
Inserting that and the interest rate into the budget constraint gives:
$127.3k = C0 + C1/1.1
Since Arlene wants the same consumption in each period, she will choose C1 to be equal to C0:
C1 = C0
Eliminating C1 from her budget constraint and solving for her equilibrium C0:
$127.3k = C0 + C0/1.1
$127.3k = C0*(1 + 1/1.1)
$127.3k = C0*1.91
C0 = $127.3k/1.91 = 66.7k
Arlene's consumption in period 1 will be:
C1 = C0 = 66.7k
Since her consumption is less than her income in period 0, Arlene is saving. The amount is $100k - $66.7k = $33.3k. With interest, in period 1 that will become $33.3k*1.1 = $36.7k. Adding that to her $30k period 1 income gives $66.7k, or exactly enough to pay for C1.