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Numerical illiteracy

We get the Boston Globe daily, so I was generally aware that there is a movement afoot to relieve us geezers of our driver’s licenses as we get older. Yesterday, an article in the Day, at least on the surface, seemed to imply that there was little evidence that the elderly driver was a threat.

The headline read: “Elderly drivers in fewer accidents than others“. The sub-headine, if that’s what it called, pointed out that “Statistics don’t change push to change law”. The clear implication was that elderly drivers are statistically less likely to get into accidents than others.

But as has been said, there are three kinds of liars, the last of which is “statistics”. The first 17 paragraphs of the story make a compelling case, if you are numerically illiterate, that the elderly driver is not more likely to get into an accident than others. According to statistics, elderly drivers account for a smaller percentage of accidents than drivers in other age groups because while licensed geezers over 75 were 7 percent of those holding a license, they were only 3.6 percent of those involved in crashes.

These and other meaningless statistics lead some clueless experts, such as Russ Rader of the Insurance Institute for Highway Safety, to say that “there isn’t much evidence that elderly drivers are a big menace to other people on the road.”

Well, I’m not yet in the older than 75 category, but my mother is. She owns a car that is over 20 years old, which she bought new. It has less than 40,000 miles on it. These days, she might average 10 miles a week. I drive at least 10 to 20 times as much as she does. If she is one licensed driver, than I should count as 10 to 20 drivers in any reasonable comparison. Lots of elderly people have licenses but don’t drive at all. They should count as zero licensed drivers. It seems fairly obvious that simply looking at the percentage figures for various age groups tells you almost nothing.

Sure enought, in the 21st paragraph, long after most readers have moved elsewhere, we get to the nitty gritty:

[O]n the basis of miles driven, which the state does not track, the GAO found that drivers age 75 or older are more likely than all other drivers to be involved in fatal crashes The GAO report did not track nonfatal crashes.

So, the long and the short of it is that if you look at the only statistics that matter, the statistics disprove the headline. Geezers may be in numerically fewer accidents than others, but if they drive, they are more likely to get in an accident.

I’m not suggesting any particular course of action regarding elderly drivers. It’s a complicated issue, particularly in our car-centric society. I am merely pointing out that we can’t debate these issues in any reasonable fashion if we don’t understand basic math. I don’t know if this inability to understand basic mathematical or logical propositions is a peculiarly American phenomenon, but it is certainly not amelioriated by newspaper articles that misread statistics to prove a point that is simply not proven by the numbers on which they rely.


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