I should have added that I was assuming a prices of production model for
appreciation. Appreciation can also be calculated in a similar way for
values, although if you are calculating by Sraffa's method, that is,
treating fixed capital as a joint product, you need a method af allocating
value between joint products.
Again all such calculations are calculations of known quantities and have
not much to do with what charge capitalists make in practice. Whether this
a worry depends on what the theroretical objective of a theory of value is.
Since it can hardly be to provide an accurate prediction of capitalist
pricing, i don't see why it should aspire to offer a forward estimate
rather than retrospective account of values.