Survivorship Bias

So I’m at the local barber shop, waiting for a haircut. It’s the kind of old-school barber shop that you see in the movies. The barbers are friendly and love to talk to the customers. People feel at home while getting their hair cut.

While waiting, one of the customers was telling the old barber about his grandfather. Apparently, the man’s grandfather worked in a mine most of his life. He apparently smoked and drank throughout his life as well. His grandfather lived to be 98 years old. “It just goes to show ya’ that none of that stuff about smokin’ and drinkin’ matters. It’s all about the hard work that keeps you healthy”, said the man proudly about his grandfather’s longevity.

I couldn't help but feel happy for the man and his proud memory of his grandfather.

But then, is this a reasonable conclusion? Can hard work protect one from the damaging effects of long-time smoking and drinking? We have good evidence that smoker’s live shorter lives, on average, than non-smokers. There is also good evidence that excessive alcohol doesn't help either. Hard work no doubt is a virtue, but what about all of the other hard-working miners who smoked, drank and died early? Their grandsons tend to not tell proud stories in barber shops of their longevity.

But perhaps the best conclusion is that statistics predict a that minority of most “at-risk” groups will survive. If 90 percent of those at risk from some danger will not survive, then 10 percent will. These 10 percent are the lucky outliers. It does not really mean that the survivors necessarily possess some quality that the non-survivors do not? However, the non-survivors do not go on to catch our attention. They are less visible. History does not remember non-survivors like the survivors. Many non-survivors may not have had the opportunity to have proud grandson’s.

However survivors are often statistical outliers. It is less romantic to attribute success to chance than to outstanding virtue.

Yet, we understandably attribute their success to more than chance. There must be a reason for their survivorship. Longevity must be due to virtue. Successful entrepreneurs must have been prescient. Celebrities must have superior talent. We could all achieve their kind of success if we could just figure out their secrets. However, the successful likely do not possess secrets that other competitors do not. Survivors are more likely to have been in the right place at the right time.

The You Are Not So Smart podcast dealt with the fascinating topic of Survivorship Bias. It is worth the listen.

Survivorship bias is our natural tendency to over-weigh the virtues and qualities of survivors, while discounting the non-survivors. An old building may happen to still stand. “They don’t build them like they used to”, many say about such a structure. However, maybe most such structures collapsed long ago. Only the outliers remain. Most new businesses do not survive. But those that do are not necessarily the best. Perhaps some are, but most are the outliers. Perhaps some successful business people, some long-lived smokers, and some celebrities achieved success due to their superior virtues, but research suggests otherwise.

We are often not even aware of the non-survivors or of their large numbers. As such, the proper perspective is not intuitive. Non-survivors will likely not be remembered by history.

We are surrounded by the successful outliers. We are naturally biased toward attributing their success to more than background statistics. It would seem that we too can be successful, live the longest, be the best, if only we knew their secrets.

A comedian once said something to the effect of, “I hope I live to be 100. When people ask me about my secret, I’ll make up something ridiculous. I’ll tell them that I ate a pine cone every day. Then I’ll see how many people start eating pine cones.”

Science is a way for filtering out the real from the apparent. It is not intuitive. As a whole, people who do not smoke out-live those who do. Moderate drinkers outlive heavy drinkers. Those who exercise tend to out-live those who do not. It is unlikely that eating a pine cone will help.