Improvement in Economy of Operation of ment in business conditions and in spite of reduced efficiency in the operation of this individual railroad, considered 'per se. It is not intended here to cast any reflections upon the managing ability on the railroad in question. The only object in mentioning the matter at all is to point out the fact that the use of the year 1908 as unity puts the road unnecessarily under suspicion of attempting to mislead the public.

In any chart where index numbers are used the greatest care should be taken to select as unity a set of conditions thoroughly typical and representative. It is frequently best to take as unity the average of a series of years immediately preceding the years for which a study is to be made. The series of years averaged to represent unity should, if possible, be so selected that they will include one full cycle or wave of fluctuation. If one complete cycle involves too many years, then

Fig. 94 the Wheeling and Lake Erie Raibroad, 1908 to 1912

It will be noticed from the upper left-hand corner of the chart that the j'ear 1908 is taken as unity. 1908 was a year of great business depression. As business conditions naturally improved in the years following 1908, there could be a legitimate question in the reader's mind whether the better showing of the railroad is due to better management or to the increase in the general prosperity of the covmtry

CURVE PLOTTING