Index Value Plot

In an index value plot, we have index values being compared as opposed to absolute or total values.  In our example graph we are basically measuring seismic activity in a region of the Pacific Ocean.  With the years on the bottom, we see that all years with a positive index, one that is above zero, we have more than average activity and that every year below zero we see less than average activity.  The reason that the average is zero on this graph is because we have standardized the variable.  Thus, our graph essentially measures how far above or below average a certain year was as far as quantity of seismic activity goes.

http://www.jisao.washington.edu/data/pdo/