In addition to this there is probably another serious fallacy which affects all three curves shown on the chart. The income figures from which the curves are plotted may not all be shown on the same basis. Men working on a salary have as net cash all the money they receive. Men in professions such as law, medicine, etc., where office rent and other expenses are likely to be very heavy, may report, as earnings, the total amount of money received without making corrections for the expenses of conducting their business. In other words, they may very possibly in this case report gross income instead of net income. Such procedure might tend to make the curves for average income considerably higher than they would otherwise be.

Complex charts made up of groups of bars as seen in Fig. 101 are much more common than they should be. This type of chart is very annoying to

COMPARISON OF CURVES

read because it is difficult for the eye to follow, through the whole series, the bars representing any one set of facts which may be of special interest. The bar method is in itself a simple one, but when the bars are combined in the manner shown in Fig. 101 the presentation becomes really more complex than if the data were shown in the form of curves.

Fig. 102 certainly brings out the information of Fig. 101 in much better form than any in which it is possible to show it by any combination of bars either vertical or horizontal. The person who is just beginning to chart data °°^5'-o''^% which he has used formerly in tabulated form is often =000 surprised to find how many inconsistencies exist in the