Junk Charts

Off-sheet accounting

For mid-week entertainment, this full-page ad appeared in the Wall Street Journal recently:

The vertical axis says "% NYSE of All Market Share Volume".  The time-line is from July 05 to beyond July 08.  The text in the black box is "Matched Market Share: July 11, 2008".

When it's so obvious, it's probably not obvious.  The big story is off the chart: what happened to the other 50% of the volume over the years?

Faced with this, one reaches for the pie chart (... almost).

Small add (8/21/2008):

Water and wine

Marketers have always argued that price signals quality; this leads to the startling idea that one should just set a high price. 

If you don't believe it, note how Coca Cola and Pepsi turned tap water into a premium-priced $1.7 billion market.  As we now know, Dasani and Aquafina are just bottled tap water.

Even if one can turn water to wine, now researchers discovered the same rule applies.  Unlike most scholarly articles, they actually published a well-made chart to illustrate their experiment.

Testers were given the same wine but told either it cost $10 or $90.  Their brain activity is measured.  The chart showed that those thinking it cost $90 (green line) had much better sensation about the wine than those thinking it cost $10 (blue).

A standard way to display this information is a data table that spells out every estimate and its standard error, plus some asterisk or bolding scheme to indicate statistical significance.  Visualization is far superior.

For more examples, see Gelman's paper or Kastellec and Leoni's paper.

Reference: "Study: $90 wine tastes better than the same wine at $10", News.com, Jan 14, 2008.

Sense of proportion

[I'm back from vacation.  Will provide my reaction to the responses to the Gelman challenge, and for those who have sent me email, I will work through them soon.]

The NYT commented on a trend among marketers to shift their advertising spending from so-called "measured" media like print and TV to so-called "unmeasured" media like product placements, contests, etc.  The following chart accompanied the article:

This construct is akin to a population pyramid; it's great for comparing two groups along one metric, say age groups between males and females.  Here, the two halves aren't comparable groups but two different metrics.  The main metric, that is, the proportion of unmeasured, is not directly depicted: the reader must figure out mentally how much of each bar the black part covers.  Also, the companies are sorted by unmeasured media spending but this leaves the measured spending with a jagged profile, confusing matters.

As for the little white slits on the gray bars, they are admittedly cute but it is difficult to compare the detailed breakdown between print, TV and other media among companies.

The following dot plot gives the two halves equal weight.  (Pink dots are measured, blue unmeasured.) It's not a very interesting graphic though. The sense of proportion is still missing.

I settled on a scatter plot which relates the proportion spent on unmeasured to the total amount of spending.  It appears that the largest advertisers had the lowest proportional unmeasured spend while the smallest (among the majors) had the highest.  (It's only a weak correlation: a linear fit yields only 16% R-squared.)

Source: "The New Advertising Outlet: Your Life", New York Times, Oct 14, 2007.

Dropped, just like that

Frank W. sent in a timely reminder of the start-at-zero rule.  This ad from Quaker Oats pitches the impossible: the smart consumer will never believe that cholesterol levels can be dropped just like that!  According to Frank's measurement, the column heights plunged 77% from Week 1 to Week 4 in this chart.

In fact, if the vertical axis had started from 0, then the drop would more appropriately appear to be 5%.  Now, even that would have been a miracle, in my opinion.

Thus, I would like to know what is a "point" of cholesterol, and what do they mean by "representative" drop.  I suppose they are asking me to call that number.

My previous posts (with commentary from readers) about starting at zero can be found here and here.