It is not uncommon to find in text-books and monographs dealing with particular periods a friendly footnote or so to the effect that currency values at such and such a date can readily be comprehended by multiplying monetary expressions by a suggested figure in order to produce the modern equivalent in purchasing power. Thus to discover the fall in the value of a sterling unit between the reign of Elizabeth and our own day we are told to multiply it by some such figure as 8 or 10. We may well be suspicious of these attempts to cut a quick way through the highly complicated question of comparative price levels, for it is common knowledge that prices in general were rising throughout Shakespeare's lifetime and that they have been fluctuating even more wildly during the last twenty years. But the short-period instability of values is the least serious of our difficulties, for it can be taken into account by the statistician.

There are three main reasons for holding that prices during Shakespeare's lifetime and those of to-day will not yield themselves to satisfactory treatment side by side. The first is that the whole range of transactions in economic life was then distributed as to the relative amounts and the relative values of commodities on a scheme so unlike that with which we are familiar to-day that, lacking a sufficient number of similar items whose prices we may compare, we are without the means of constructing a general price ratio; even approximate results are unattainable.