© January, 1996
used by permission
No one should imagine that this is a simple subject. Public data are unreliable, and comment is often ill-informed or biased. There are many arguments and counter arguments which need to be understood fully as the study evolves. There is important reading to be done, for which selected references at the end of the report may be a starting point.
That said, we will nevertheless try to reduce the subject to its bare essentials, using graphics to make the main points. [Note: Graphs can be seen full size by clicking on the image with the right mouse button and selecting "view."]
Complete Version (no breaks between sections)