Final Answer: Peter and Blair must accumulate approximately $658,864.37 by retirement.
We can solve this problem by calculating their retirement income shortfall, adjusting for inflation, and determining how much money they will need to fund that shortfall over 25 years.
Step 1: Calculate the annual income shortfall.
Desired retirement income = $97,514
Expected retirement income = $71,000
Annual shortfall = $97,514 - $71,000
Annual shortfall = $26,514
This means Peter and Blair need an additional $26,514 per year in today's dollars.
Step 2: Adjust the shortfall for 34 years of inflation.
Since inflation is expected to average 2% annually, the amount they will need in retirement will be higher.
Future shortfall = $26,514 x (1.02)^34
Future shortfall = $51,985.36
Therefore, their annual income shortfall will grow to approximately $51,985.36 by retirement.
Step 3: Calculate the amount needed at retirement.
Peter and Blair expect to need retirement income for 25 years.
Their investments will earn 8% annually, while their required withdrawals will increase by 2% annually due to inflation.
We can use the present value of a growing annuity formula:
PV = Payment x [1 - ((1 + g) / (1 + r))^n] / (r - g)
Where:
Payment = $51,985.36
r = 0.08
g = 0.02
n = 25 years
Substituting:
PV = $51,985.36 x [1 - (1.02 / 1.08)^25] / (0.08 - 0.02)
PV = $658,864.37
Final Answer: $658,864.37
Peter and Blair must have approximately $658,864.37 saved when they retire in 34 years to cover their projected retirement income shortfall for 25 years.
This assumes their first withdrawal occurs one year after retirement, subsequent withdrawals increase by 2% annually, and their savings earn an 8% annual return.
The key idea is that we must account for both inflation and investment growth. Inflation increases their future expenses, while investment returns help their retirement savings last longer.