4th March 2016

Survivor Bias

Or what I prefer calling sky diver bias.

As we ready ourselves to bring our baby Max for his second round of vaccinations, it’s hard not to question whether we’re doing the right thing. It’s just a big drag to take him to the pediatrician, knowing he (and we) are in for another shriek, and a day of whimpering. If you’re an anti-vaxer convinced it may cause autism, (and we aren’t) then declining is even more understandable.

I wrote about the vaccine debate a year ago (It’s a wonderful Vaccine) but it’s more real when your own kid is on the end of the needle. As I look back at that writing, the only thing I’d add would be some lines on survivor bias. Sorry to nerd out, but I thought I’d type a little addendum. Rather than survivor bias, I sometimes call it sky diver bias, just to hammer home the point.

Have you ever met someone who had a bad time sky diving?

I haven’t. The sky diver selfie is a classic image that pops up regularly on fb and it does seem like the greatest high on Earth. I, however, don’t sky dive, because I know that those who had a bad time are grossly underrepresented. Nobody posts selfies when their chutes don’t open for obvious reasons.

This same kind of bias applies to vaccines. Kids with diphtheria and the like are massively underrepresented in our brains. We just don’t meet them or read about them any longer thanks in part to vaccines. Now a new kind of survivor bias is emerging. Parents who choose no vaccines generally have kids who survive and perpetuate a perspective that vaccines aren’t needed. If people with tetanus were among us a bit more, however, I think the debate would be muffled considerably. In countries where these diseases are still prevalent, people line up for vaccines. Knowing this, Max will still receive round two.

Many of our perspectives are shaped by survivor bias. When you’re bored, try to consider other areas in life where this may apply. If you grew up in the 70s you probably remember sitting on the front seat unbelted. Riding on the arm rest between my folks was my favorite spot in the car as a kid. My second favorite spot was the rear dashboard. Perhaps you, like me, pine for those good old days. I can’t tell you how bummed I am about raising a kid today with a car seat… that faces backwards no less! He hates it too. But knowing about survivor bias makes us play along. I survived with my fond memories, but others didn’t and we don’t hear from them. Cows on a farm think the farmer is a nice guy, because they never hear back from their friends that leave the pasture.

Survivor bias applies to heroin and meth use as well. I suspect most who try these, initially do so in the company of cool, happy, fun people. They don’t meet the patients I meet in ERs with massive abscesses, and especially not those who OD.

Few movies are made about the first soldiers to die on the beach. Does the hero in any war movie ever die? Survivors with captivating stories return home to parades and medals, and inspire the next generation of warriors who may not yet know about survivor bias.

Next time you hear a gun control debate, listen for mention of this kind of bias. What would be the discussion if 250,000-300,000 US dead in a decade could speak or vote? Not taking sides. Just sayin’.