Page:Popular Science Monthly Volume 31.djvu/791

Rh 100, and the average decline in the prices of these same articles for the year 1810 was found to be 20 per cent, the index number for the year 1800 would be 100, and for the year 1810, 80.

The difficulties in the way of obtaining satisfactory averages from comparisons of prices at different periods by the above or any other methods are, however, almost insuperable; so that it may well be doubted whether the determination of an average of general prices is ever within the bounds of possibility. Quotations for a given day, or month, do not necessarily show the average for the year; and, in like manner, the selection of a limited number of articles for comparison can not insure correct conclusions respecting the movement of prices in general. All methods of comparing price variations which content themselves with mere average quotations of different articles, and which do not pay due regard to the relative importance of each article in the domestic and foreign commerce of a country; which, for example, allow a change of 80 per cent in the price of an article like cochineal, of which the value sold in any one year is small, to balance a change of 2 per cent in an article, like sugar, the value of which annually sold is enormous, are also in a great degree deceptive and worthless; and even when in the comparison of prices, the importance of considering relative quantities is fully recognized, the data for ascertaining these relations are extremely uncertain and questionable. The utmost of service that all such tabular comparisons of prices, even when prepared with all desirable qualifications, are capable of rendering, would, therefore, seem to be limited to the affording of important inferences respecting variations of prices, or to the showing