When the readers are likely to be familiar with this form of chart.

4. When the usual arithmetic chart would present a misleading picture of movement.

5. For occasions when there are no minus figures included in the time series.

Note; If it is desired to present a complete picture of both rote of change end amount of chonge the dato con be presented on componion charts, one with a logarithmic amount scale and the other with the usual arithmetic scale.

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Secondory scale of uniform rotes of change

SCALE SELECTION. Logarithmic amount scales should be so selected that the curves will be well placed on the grid. As

there is no zero line to serve os a base for comparing trends, considerations of the zero line ore not applicable to rate-of-change charts.

In rote-of-change charts, it is often helpful to provide a secondary scale indicating uniform rates of change. Such scales are constructed by means of straight diagonal lines radiating from some point of origin las shown in the illustration at the right).

Multiple amount scales are more appropriate for rate-of-change charts than for arithmetic charts because in the former the movement of the curves is compared and not their position relative to a base.

Note: in order to take full advantage of the scale range, the verticol scole numerals usuolly printed on a chart sheet may be multiplied by any constont foctor but integers should be chosen so that the scale subdivisions will not indicate inconvenient fractions.