Weighted averages are of very great importance in most studies relating to the cost of living, and they could be used in other work much more widely than at present if their importance and utility were more generally understood. It is unfortunate that in Fig. 95 the term "relative prices" is used in the lower portion of the chart as the key for the dotted line. The simple averages show relative prices also and the term "relative prices" means practically nothing. The dotted line could more properly be referred to by the term "weighted averages" as used in the title at the top of the chart.

Fig. 96 is an example of a type of chart which can be of great assistance to the chief executive of any corporation having a business

106 GRAPHIC METHODS

seriously affected by the ups and downs in financial conditions affecting the country as a whole. In this chart, a study has been made of supply and demand in the hope of getting some basis for prediction in regard to periods of financial depression. The various factors which might affect prosperity in steel construction work are assembled here on one chart so that the whole situation may be studied conveniently and thoroughly. In a chart of this kind some estimates and approximations must be made because it is usually impossible to obtain accurate data to the extent desired. For work of this nature it will ordinarily be found that a little "horse-sense", used in making estimates for missing data, will permit the construction of a chart giving an astonishingly large number of suggestions useful in determining the policy of a business, so that expansion and contraction may be in harmony with the basic financial conditions of the country.