STOCK GOODIES PLAYS OF THE WEEK

[BoomPickens]

Price Scaling

There are two methods for displaying the price scale along the y-axis: arithmetic and logarithmic. An arithmetic scale displays 10 points (or dollars) as the same vertical distance no matter what the price level. Each unit of measure is the same throughout the entire scale. If a stock advances from 10 to 80 over a 6-month period, the move from 10 to 20 will appear to be the same distance as the move from 70 to 80. Even though this move is the same in absolute terms, it is not the same in percentage terms.

A logarithmic scale measures price movements in percentage terms. An advance from 10 to 20 would represent an increase of 100%. An advance from 20 to 40 would also be 100%, as would an advance from 40 to 80. All three of these advances would appear as the same vertical distance on a logarithmic scale. Most charting programs refer to the logarithmic scale as a semi-log scale, because the time axis is still displayed arithmetically.



Verisign, Inc. (VRSN) price scaling example chart from StockCharts.com

The chart above uses the 4th-Quarter performance of VeriSign to illustrate the difference in scaling. On the semi-log scale, the distance between 50 and 100 is the same as the distance between 100 and 200. However, on the arithmetic scale, the distance between 100 and 200 is significantly greater than the distance between 50 and 100.