Page:Graphic methods for presenting facts (1914).djvu/94

 a uniform rate of change on a percentage basis. A plotted line representing a uniform rate of increase from year to year on a percentage basis may be seen in the curve given in Fig. 121.

The untrained reader of curves will probably not be able to tell instantly what made the flat portion of the curve in Fig. 69 during the year 1907 to 1908. One of the chief advantages of the curve method of presenting information is that a curve forces one to think. A little thought here will at once bring out the fact that the flattening of the curve was caused by the 1907 panic. Though the panic started in October of the year 1907, the year 1907 was really one of the most prosperous years the country has ever known. It would be more fitting if the panic were called the 1908 panic, since the main effect of the panic came in 1908 rather than in the year 1907. It can be seen that the Princeton men had their incomes reduced during the year 1908 so that the average fell below that of 1907. By looking along the curve it will be noticed that though there was a larger yearly increase in salary after 1909, salaries at the end of 1911 had not attained the point which it would seem they would naturally have reached if no panic had occurred at a time so shortly preceding this date.

The Philadelphia Commercial Museum

Fig. 70. Cotton Goods Production, Import and Export for the United States. Values are Given in Millions of Dollars

The order of years here reading from right to left gives the first impression that production is decreasing. Compare this illustration with Fig. 71