DATA to Insight

The Dow-Jones Industrial Average

For about a decade I have been making datagraphics out of the daily close reports of the DJIA. Although the data now number over 31,000 observations, the pattern is not very complicated, and its lessons are sobering.


Because the overall behavior is multiplicative, the unlogged data appear to show a recent explosion.


When the data are logged we easily see an overall pattern of periods of fairly steady grown interspersed with periods of "doldrums" that appear to be centered near powers of 10.

Histogram of powers-of-10

When the logged data are binned by a histogram we easily see how the daily close tends to cluster around 100, 1000, and 10000, and the red density function highlights this behavior. Whether this clustering is a function of mass psychology is an interesting speculation.


A simple forecast based on exponential smoothing shows that the Dow will probably begin to rise more consistently someday, but no one is entitled to assert when this might be...