Always Be Comparing Thy Numbers

About a year before the corona pandemic, I wrote a much-read and well-publicized article about perspectives: “Let’s Find Out — Or the Power of Reference.”

I believe it was the first time I was cited by the Financial Times’ masterful Alphaville section.

In it, I mixed the core insights of Hans Rosling’s Factfulness with another book I had just read: Bobby Duffy’s The Perils of Perception: Why We’re Wrong About Nearly Everything, based on countless surveys from the polling firm Ipsos.

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The basic point is this: numbers should never be left to fight for themselves. Numbers about anything should never be reported without a reference point, without a perspective, without a comparison to show me how much that is. This is what I wrote:

“a statistic may never be left alone, Rosling maintains, but must always be compared to other relevant numbers. What share of its total category does this statistic represent? What was it last year, 5 or 10 or 20 years ago? Is there some self-evident change in associated behavior that is relevant or ought to explain it? A century ago street cars used to kill and injure hundreds of people every year, but since very few American cities make use of street cars today, the casualty is fortunately much lower. If we keep in mind that miles travelled by cars far outnumber miles travelled by street cars, reporting the number of street car deaths — while probably correct — entirely miss the point when discussing traffic safety.”

Tim Harford’s BBC show More or Less has made this into an art form (can’t wait for his How to Make the World Add Up, released in September!)

Few people have an encyclopedia of updated statistics over every conceivable topics — which means that when a writer supplies a number without context or long-term perspective, (s)he taps an unknown reference point in the reader’s mind. 561 dead people is an unimaginable tragedy to most people. Probably the extent of my extended friendship and family networks. Picturing it, I see before me — horror-movie style — the lawn full of corpses. That’s a lot.

561 was the number of people who died from plane crashes in 2018. Does that same number of corpses seem like a lot? How about when I tell you that the year before that same number was 59. Almost a nine-hundred percent increase!, as a news article in Forbes nonsensically reported.

What if I told you that the average number of deaths from plane crashes between 2006 and 2010 was almost 800? Now, 561 don’t seem that bad; good job, airline industry!

In 2018, 4,233 million passenger miles were flown. 4,3 billion people (not necessarily different people as the same person can take several flights in a year) — travelled on 37,800,000 flights. 15 of those flights crashed, leading to the death of 561 people.

Again, now those 561 deaths don’t seem like very many. Perspectives matter, and the responsibility for properly conveying the meaning of numbers lies on us writers. Do your job, people, and report numbers with their relevant perspectives!

Presciently regarding the corona debacle, here’s what a wrote in that piece — hypothetically, of course:

Here’s another example. If I told you about 23,000 individual deaths and spent a brief 10 second on each of them, going through the list would take me almost three days. On a personal level like that, 23,000 deaths is an absurd, insane, catastrophe-style event that few people are emotionally equipped to handle — essentially the size of my hometown, wiped out in a single year. If I told you those 23,000 deaths were due to antibiotic resistant diseases in the U.S. last year, the pandemic scenarios working through your mind quickly escalate. That many! Let’s find the nearest bunker!

If I then told you that cancer and heart diseases (each!) claim the lives of about 20x that, the fear of lethal apocalyptic germs consuming the world ought to quickly recede. Oh.

Looking at the unprecedented reactions to the corona pandemic this year, it seems nobody had read my article — shocking, I know! What we did wrong in the pandemic was to not compare our numbers. We saw deaths — and we panicked.

The risk for young people to die or get seriously ill from the disease was much lower than risks we ordinarily take without thinking about them. For those below the age of 65, corona was a danger on the scale of driving 150 kilometers to work: routine. Yet, everyone freaked. People forgot to heed Rosling’s call to put numbers in perspective.

Never trust numerators without denominators or past-year comparisons. Never accept an unaccompanied statistic. Ask instead: “is that a lot”?

You’ll be surprised to find how often it isn’t. Always Be Comparing Thy Numbers.

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Writer, editor, and student of money past and present. Here: mostly off-topic stories, personal finance-musings, worldly observations and Reykjavík reflections.

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