Mortgages and Life
I've been working very hard over the past two days on a spreadsheet which emulates the 1988/1989 interest rate change, and with a couple of handy excel/google spreadsheet functions I managed it. I now have a model for repayments of a mortgage that is a fixed-rate for five years which then exits straight into May 1988 (@7.5%) The pattern then increases till the mortgage reaches 15% (which is an unrealistic level again) within a year and drops back down.

What's interesting is that we could still afford it (for the target amount).

PMT(InterestRate, NumberOfPeriods, Principal, FutureValue, PaymentsDue)
Calculates repayments for n per year

CUMPRINC(InterestRate, NumberOfPeriods, Principal, Start_period, End_period, PaymentsDue)
The CUMPRINC function calculates the amount of principal repaid in between a specified range of periods.

CUMIPMT(InterestRate, NumberOfPeriods, Principal, Start_period, End_period, PaymentsDue)
Similarly the CUMIPMT function returns the interest paid in between a specified range of periods.