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Bad Charts.

Best's Worst Pie Chart Ever
Backward in Time and Other Errors
From Bowling Alone
Just Plain ChartJunk
More ChartJunk
NYTimes Donuts
Petraeus testimony
All Clutter:
Time Series Data Distortion
 

The Worst Pie Chart Ever:
 

Problems with this chart:

• a clear violation of Pie chart Rule #2: pie charts are for data that add up to a meaningful total.
   

Reported by Joel Best.
For more on numeracy, go to www.StatLit.org/Numeracy1.htm

Backward in Time and Other Errors:
 

Problems with this chart: Time is displayed backwards on the X-axis. 3-D effect: does the scale match the front or the back of the bars? Scaling: the high values on the community college scale minimize the important variation in the other two series.

Source: Illinois Board of Higher Education, Illinois Higher Education Annual Report (July 2002), 24

Figure 3.16: Revised Enrollment Chart:

From Bowling Alone

Problems with this chart:

• unnecessary 3-D effect.

• The chart does not display meaningful data (the most important data are actually represented by the arrows on the bars, not by the height of the bar).

• The chart is not self explanatory [the letters on the bars reference the textual explanation].

Source: Robert D. Putnam, Bowling Alone (New York: Simon and Schuster, 2000), figure 47

Figure 3.5: Revised Chart, with Data from Text:

Just Plain ChartJunk:

Source:  Kristin E. Smith, Loretta E. Bass, and Jason M. Fields. "Child Well-Being
Indicators From the SIPP" Population Division Working Paper No. 24
U.S. Bureau of the Census. Washington, D.C. April 1998

More ChartJunk:

From: http://himpflcogirdbvb-mbh.freeyellow.com/chart_of_the_week.html

These charts have something to do with futures trading: (click on thumbnails)

source: : http://himpflcogirdbvb-mbh.freeyellow.com/chart_of_the_week.html

NYTimes Donuts

Source: New York Times: 3/14/08: "This article will appear in this Sunday's [3/16/08] Times Magazine."

Problems with this chart: Charles Blow usually does a better job with the Times graphics. In this case, he asks the reader to draw comparisons across what are in effect 18 pie charts.  Roughly estimating the numbers from the chart, and just using Obama's share of the primary vote,  this is my revision: Notes:  There is some method to the sorting here, but it might have been better to sort by the date of the primary to avoid the implication that the city\rural divide is increasing. (and with a smaller font):

Petraeus testimony

In his Senate testimony defending the progress in the Iraq war on April 9, 2008, Army General David H. Petraeus presented several charts, including the one below summarizing the operational readiness of the Iraqi army and police battalions.  Glenn Kessler, of the Washington Post comments on several of the charts here:

The stacked bar chart represent the number of battalions at each stage of readiness, with ORA 1 being the highest stage.

The problems with the chart are the following:

• Because the most meaningful comparisons are across time, and not between the National Police and Iraq Army, it would have been better to construct this chart as a two panel display, with the three time periods adjacent to each other, within the police and army panels.
• "The Battalions in the lead" annotation is undefined.  In the first panel it seems to refer to ORA 1 and ORA 2 readiness, but in the second panel, the bracket stretches down into the ORA 3 level.
• The stacked bars should have been sorted in reverse order.   The March 2008 Army bar is much taller than the January 2007 Army bar, but mostly because of the increased number of battalions at the lowest levels of readiness.  Indeed, it looks as if the most crucial component of the bar -- the dark green at the top --is actually smaller in 2008 than in 2007.
• Example of ORA 4 readiness training.

Estimating the numbers from the graphics,  the following chart shows how the "army" side of the chart could have been constructed.  Notice how the relatively modest increase in the number of battalions at the two highest levels of readiness.

All Clutter:

Not content with the distractions and distortions made possible by the use of 3-D effects, charters sometimes feel the need to add all sorts of other Chartjunk to a graph.  In the graphics on the left, Kevin Phillips is trying to make the point that income is more inequitably distributed in the United States than in other countries.

Note the extraneous features of this in this graphic.

• A completely irrelevant map of the world.
• Two entirely different kinds of 3-D charts displayed at two different perspectives.
• Country names are repeated three times.
• To display 24 numeric data points, 28 numbers are used to define the scales.
• The countries are sorted in no apparent order (not even alphabetically).
• Note the use of the letter " I " to separate the countries on the bottom chart.

While it might be possible to design a better graphical display for these data, a table does the job quite nicely:

*Kevin Phillips, The Politics of Rich and Poor (1991: Harper Perennial), 9.

Time Series Data Distortion

This is a time series chart originally printed in a public policy textbook authored by four professors of political science employed by three public universities. 

From these data they conclude:

"There is some evidence that the cost of higher education may not have escalated so much... Figure 9-12 reflect the average cost for tuition, room, and board as a percentage of median family income from 1964 to 1995.  While private institutions have increased costs substantially, public university costs have remained constant.  This indicates that the increased costs associated with higher education may be quite reasonable when compared to family income levels." (Cochran, 346-7)

Note the ways in which the authors have understated the rising costs of public university education.  First, the costs are deflated not by adjusting for the consumer price index but by median family income -- especially for the years after 1982, median family income rose much faster than the consumer price index.  Second, graphing both the private and public data on the same graph enlarges the scale on which the public data is displayed.   It's hard to tell from the graph, but between 1980 and 1995 it appears that public university costs increased from around 11% of family income to near 15% -- in effect, the share of family income going to public university costs has increased by a third. The third way of minimizing the cost increases that have occurred since 1980 is to extend the time series back to 1965.

A completely different picture emerges if one were to compare the rate of increase in public university costs to the rate of increases in other sectors of the economy.  On the left, we see that from 1981 to 1999 -- over the lifetime of today's college student -- public university costs have risen faster than any other sector of the economy.  Faster even than rising medical care costs. In addressing the topic of health care inflation,  the same authors note that: "Cost escalation in the medical field has been constant," and spend four pages of text addressing the reasons for the increases. (pp. 268-72). 

Clarke Cochran et. al. American Public Policy: An Introduction (1999: St. Martin's Press),