"Ronald Raygun" wrote
While it was easy enough for you to make up a set of value movements
which made the 2007/8 value proportions the same as the income ones, ...

"Tim" wrote:
It's not a matter of "making up" the value movements, ...

"Ronald Raygun" wrote
It is if I use "make up" in the sense of "posit ficticious
values for". Naturally it goes without saying that
you can't make up *arbitrary* values for f and g,
the two years' inflation factors. There is only one
pair of values which will work to achieve the effect
you wanted, and of course it must be calculated.

But I didn't calculate any inflation factors!!

I first calculated the latest yield:-
In 2007 : yield = 17/75 = 22 2/3%.

Then I applied this latest yield to the income on each property:-
Property A value = 20 / 22 2/3% = 88.24.
Property B value = 15 / 22 2/3% = 66.18.
Property C value = 17 / 22 2/3% = 75.00.

No inflation factors in sight anywhere!


"Tim" wrote
... but rather *calculating* them from their yield.

"Ronald Raygun" wrote
Well, I suppose you can do it by working out the yields first, but
that seems a bit long-winded. How I would do it is to observe
that the two three-way ratios 100fg:60g:75 and 20:15:17
must be equal, which boils down to solving the three equations

[1] 75k = 17
[2] 60gk = 15
[3] 100fgk = 20

for f and g, which *can* be done by calculating k first (which
happens to be one of the yields) from [1], then using that in
[2] to work out g, and finally using that in [3] to work out k,
but it can also be by eliminating k algebraically, calculating g
directly by dividing [2] by [1], and f by dividing [3] by [2].

60g/75 = 15/17 = g = 1.103
100f/60 = 20/15 = f = 0.8

"Ronald Raygun" wrote
... the underlying assumption that the value inflation rates are the
same
in each of the three locations in any one year is a pretty unrealistic.

"Tim" wrote:
Of course, but in the absence of further information (the question
had no other data), it's got to be the best assumption, hasn't it?

"Ronald Raygun" wrote
It's the only possible assumption, which
makes it simultaneously the best and the worst.

I disagree. You could instead assume that the yields are constant
in each location, and so the values are also constant. But I don't
think that is as good an assumption as the one I made earlier...


"Ronald Raygun" wrote
But since it is objectively bad, might it not be better than solving the
problem on the basis of it, to throw up one's hands in warning and
say that the answer will be silly so there is no point in working it out?

The OP asked the question, so s/he obviously wanted to see an answer!