Linear Scale Chart
A linear scale chart is measured by dollar value, and it is shared throughout the entire chart. It lacks communication on the rate of change. So while the overall net financial accumulation might seem to be increasing but the rate of increase might be slowing down, and yet it is not easy to tell with a linear scale chart.
Logarithmic Scale Chart
A logarithmic is plotted so that the dollar value in the chart are not positioned equally from one another. It is plotted in such a way that the equal percentage changes are plotted at the same vertical distance.
Commonly recurring percentage changes (change on change) are represented by an equal spacing between the numbers in the vertical distance. For example, the distance between $10,000 and $20,000 is equal to that between $20,000 and $40,000 because both scenarios represent a 100% increase in price. An upward sloping chart may give a false sense of security that their overall financial health or investment performance is improving while in fact, it is increasing at a reduced rate.
Summary
Linear Scale Chart - the height of the chart measured by dollar value.
Logarithmic Scale Chart - the height of the chart measured by percentage changes.