You appear to running an older version of your browser, which this application does not support and many features are not unavailable. We recommend viewing this site using the latest version of Google Chrome or Firefox.
There is a magic in graphs. The proﬁle of a curve reveals in a ﬂash a whole situation — the life history of an epidemic, a panic, or an era of prosperity. The curve informs the mind, awakens the imagination, convinces.