In Fig. 143 the percentage who married at each age is given in figures at the top of the chart. By observing the figures at the top of Fig. 143 and the figures at the top of Fig. 150, the method for plotting a cumulative frequency curve will be apparent. Beginning with the percentages for the later ages in Fig. 143, the figures for the various years are added cumulatively to give the figures seen at the top of Fig. 150. The figures and the curve of Fig. 150 thus show the per-

FREQUENCY CURVES

centage ^Yllo married at ages greater than any specific age selected from the horizontal scale of the chart.

Fig. 151 gives an example of a class of information which can be sho^^'n to very great advantage by the use of cumulative frec^uency curves. In an annual report of a railroad a tabulated statement of the number of miles of different weights of rail in use at the end of the fiscal year makes the information difiicult for the stockliolder to interpret. Putting the data in the form of a curve like Fig. 151 lets the stockholder see at once just what conditions are on his road, in so far as rail weight is concerned. Thus, in Fig. 151, the stockholder may see at a glance that a very small percentage of the rails on this railroad weigh in excess of 75 pounds per yard, and that only about half of the rails weigh niore than 70 pounds per yard. In order to compare difi^erent years it would be well to have a chart of this kind printed in the