\

-'/

<

,,«.<

^^--

T*or

o«5-

of_55

'■'-

-^

II-

-'''

'/

en %, ff iJ! E

no leo

uio

I70

izo

Uk I i k I \ i t I t I iAi

Includes a * loo loan

Fig. 137. Loans Each Month Made to Employees of a Large Industrial Corporation and Amounts Paid Back Each Month. Number of Accounts Opened and also Number of Accounts Closed Are Shown on a Cumulative Basis

Note how the curve for repayment lags behind the peaks and valleys of the curve for loans. The extent of the lag gives a good idea of the length of time loans are outstanding. This illustration is for the same loan department shown in Fig. 136

Great care must ordinarily be taken in determining to just how great an extent the element of "lag" enters in. The best way of determining this is to plot the two curves on separate sheets of transparent bond paper, tracing paper, or tracing cloth, plotting each curve to a separate scale, if necessary, so that the peaks and valleys in the

1.58 GRAPHIC METHODS

two curves will be as nearly as possible at equal distances from the zero line. It is difficult to prove a "lag" unless the scales are selected so that the peaks and valleys in the two curves are at the same height above zero. After the two curves have been plotted separately to carefully selected scales, they may be superimposed and read through both sheets of paper held in front of a bright light. xVs the horizontal scales for the two curves are the same, it will be found, if the curves depend upon each other without the element of "lag." that the peaks and valleys will almost coincide. If there is "lag," it will be found necessary, in order to make the peaks and valleys coincide, to shift one sheet horizontally over the other so that the horizontal scales disagree.