28 March 2010 ~ 1 Comment

How to Live Longer

Took a crack at re-imagining an infographic from the Economist, from an article on life expectancy in America.

The study, published in PLoS Medicine, looked at four preventable risk factors: smoking, high blood pressure, elevated blood-glucose levels and being overweight. It then examined how these risk factors reduced life expectancy in eight population groups. … (or, put another way, could expect to gain those years if they were to live healthier lives).

Here is the original graphic:

From the title of the chart, I was expecting lifetime measured in years.  Scanning the horizontal axis were numbers in the single digits, off by a factor of 10 however they were close enough that it could be part of a surprising conclusion – perhaps life expectancies for some segments of the population were far smaller than I had imagined?  At the bottom of the chart, this would mean some life expectancies in the 30s and 40s, which is clearly incorrect.

Now searching the chart for clarifying data, I read the subtitle which explained the bar chart values.  Although to truly understand the values one has to do the math – add the “at-birth” life expectancies (shown in the left-most column) to the potential years gained (“value” of the bars).

It also seemed the exception that the male/female difference was significant enough to warrant adding so much contrast to the chart (the blue/yellow per-gender breakdowns).

Having just finished Wong’s Wall Street Journal Guide to Information Graphics, I challenged myself to simplify the chart and improve the understandability.

Lots of changes here:

  • The major difference between the two charts is that I’m using a stacked bar to represent the additional life expectancy gained by mitigating the preventable risk factors.  It allows the chart to be expressed at a scale one might expect when thinking of life expectancies in America (i.e. total years, somewhere above 70).  It also helps you understand the baseline life expectancy for the group combined with the relative potential improvement.
  • The national average is now presented with additional contrast, so it’s clear where each group stands relative to the baseline.
  • I chose not to label the horizontal axis from 0 – 60, assuming that readers  would understand that life expectancy is given in years.
  • The male/female discrepancies are averaged out, which caused one change in the sort order.
  • Potential gains are called out on the rightmost side of the chart, as I wanted it to be clear that the sort order was from the most potential gain to the least.

Room for improvement:

  • The most important area for improvement I see is that the title implies the “how” will be prominently featured, when it’s a footnote (literally).
  • There is no legend for the chart.  I’m relying on the implication that life expectancy is frequently communicated in years, and that the rightmost label is linked to the size of the darker-shaded stacked bar segment.  This appears to be the riskiest part of the overall change?

    Having spent a few hours on this, I have a new-found respect for those info-graphing as a day job!  Very fun, very challenging.

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