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QR for Dying is Dying for QR

Nathan Grawe
published Apr 24, 2014

I was recently pointed to a Bloomberg slideshow on how Americans die. The piece has high production value and includes a good bit of interesting data on the causes of deaths in America from the 1968 to 2010. So far, so good.

However, the curious thing is that the text often contradicts the data. For instance, the first graph includes a caption that notes that mortality rates have dropped 17% over the period studied, but that "it looks like the progress stops in the mid-1990s." The data, on the other hand, report that the mortality rate fell almost 8% from 1995 through 2010. In other words, over 45% of the drop in mortality was experienced in the 36% of time following 1995. Far from gains "stopping" in the mid-1990s, we've apparently done better in that time.

That we've made progress in mortality since 1995 is all the more amazing given two facts. 1) Death is ultimately inevitable: As we eliminate deaths, those that remain will be awfully difficult to avoid. 2) As the second slide shows, the population aged considerably in recent years.

In another instance (slide 10), the authors note they are surprised by the fact that mortality among those ages 45-54 has been steady since 2000 because "cancer and heart disease...have become much less deadly over the years." This caption is immediately over a graph showing that deaths from these causes in this age group have actually increased over this time period.

Slide 13 is a more common mistake. The authors assert that cars generally kill younger people, but fail to note the the younger age groups include 20 birth cohorts while the older groups include only 10. Little surprise there are about twice as many deaths in the younger groups in recent years.

I think we can understand this kind of problem as a form of confirmation bias. We all tend to see evidence for what we are looking for. Now, in this case, it's ultimately evident that the authors saw evidence for their priors that really wasn't there. But this is just a reflection of our flawed humanity–we are prone to seeing evidence for what we believe even when the evidence contradicts our views. What I appreciate about QR is that it at least provides a chance that others might more readily correct our error. Better yet, maybe we can learn to see our own errors and re-evaluate our priors.

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