Taking money (which need only be a money of account for this purpose, and we could equally well take wheat) as our standard of measurement, let the expected percentage appreciation (or depreciation) of houses be a1 and of wheat a2.

以货币（为此目的只需记账货币，我们同样可以采用小麦）作为衡量标准，设房屋的预期升值（或贬值）百分比为 a1，小麦的预期升值百分比为 a2。