Alternative to captions

According to The Economist, India is held back economically because it has a weak middle class.

The article is 3000 words and has three graphs. How to connect the parts of the text to the appropriate graphs? Numbered captions are one standard technique, but keeping the figure together with a legible caption can be a challenge.

Running the figures inline and referring to them as the next figure or the figure below can work but has issues for multiple columns and page breaks.

A convenient solution is to place a figure number in the chart and use text like (see chart 2).

This works especially well with charts that are largely self documenting.

Compare to expectation

Spotify dominates streaming music, which has been a good thing for the music business.

This domination is even stronger than we might expect. The sizes of top ranked collections, for example the largest cities, are often related by a power law. This observation is called Zipf’s Law.

The number of Spotify subscribers is substantially larger than Zipf predicts.



Stacked area chart

Bitcoin is not the only digital currency. An article in The Economist discusses the most popular crypto-currencies. There are now approximately 1492!

The growth of these increasing number of currencies has reduced the market share of bitcoin.

As is usual with area charts, it is easy to follow the base area and the top area, but more challenging to understand the others. Bitcoin is dropping rapidly and now well under 40%. The other basket of currencies is increasing and now amounts to approximately 30%

The data source provides an alternate presentation, an overlapping area chart.

With this display, it is easier to follow the individual coins, but the chart includes too many of them. More important, almost all area charts are the stacked variety, so this one might be misinterpreted. It would probably be better to use lines.

It can be a bit easier to see which coin is most eating away at Bitcoin be reversing the stacking order.



Use relevant evidence

In October 2017, the Council of Economic Advisers, an agency within the office of the President, released a short report on the effect of a large proposed corporate tax cut on wage growth. The only graphical evidence included is

The presentation is clear, but a graph like this raises the obvious questions: Are these countries similar to the United States? What is significant about these four years?

Presumably the CEA has access to more clearly relevant data.

An analysis by the Economic Policy Institute comes to a very different conclusion. It includes this graph

The evidence is less compelling. You could argue that the 1986 corporate tax cut led to a modest increase in compensation, perhaps through productivity growth. Or perhaps the tax cut interrupted the decades long decline of compensation growth. In any case the United States has not experienced a compensation growth of 2% or more for at least 40 years.