When an industry is imploding, lets focus on a metric that remains constant

February 7, 2013

(This article was originally published at Junk Charts, and syndicated at StatsBlogs.)

Augustine F. (@acfou) was not amused by a set of charts made by the Bureau of Labor Statistics, via Business Insider (link). Here's one of them:


The article's message is that the book, periodical and music stores industry has shrunk drastically (over 50%)  in the last 10 years but unless you spend time studying the chart, you're not likely to get this picture.

The bubbles are going right and up, which usually is indicative of an increasing trend. What is tripping us up is the employment level occupying the horizontal axis rather than the expected time dimension. The only real way to see the plunge in employment is to focus on the horizontal axis, and to notice the deepening color of the bubbles.

Redo_books1The chart is actually a scatter plot of number of firms versus number of employees. The slope of the line gives us the number of firms per employee, which is also unexpected since the usual metric is its reciprocal, the number of employees per company. However, since the slope is essentially constant, highlighting this number is pointless. While the industry is collapsing, the average workforce of the surviving firms has remained more or less the same.

I added a cone to the chart to visualize the narrow range in which the employees per firm varied during the past decade.

As if it's not confusing enough, the reciprocal of the slope is coded to the size of the bubbles on the chart. This requires a legend to explain.  All of this means that readers' attention is directed to the average work force metric, instead of the drop in employment.


The following indexed chart shows that the number of employees and the number of firms dropped in step during the ten years. Both dropped about 55% during the decade. This just confirms that the average employee per firm metric is not meaningful.


If you follow the link to the BLS analysis, you'll find some other interesting data, namely the "internet publishing" industry. Does it make sense to talk about the drastic decline in traditional publishing without talking about the rise of the "substitute" industry? The chart below shows that the new jobs created in Internet publishing filled almost all of the hole left in the traditional publishing industry. The decline from 2009 on may not be specific to the industry; it could just be the Great Recession. (As defined, I don't think the two industry sectors are exactly what I'm looking for, but it's close enough.)




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