Failure Theory

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I proposed to my wife at the top of Mt Shasta. It was my first time climbing a mountain. We joined a group climb and early one morning, roped ourselves to each other and headed up. Not too far below us we could see a very long and very deep crevasse in the ice. We made it to the top. She said yes. And the rest is history.

Years later I read the book Deep Survival which discusses human survival in extreme conditions. One point the book makes is that climbers tethering themselves together is a dubious value proposition. On one hand, if one person slips and cannot arrest their fall there is a chance that the collective efforts of everyone on the line can save them. On the other hand, the chance that somebody who did not slip is pulled down is also much greater.

Furthermore, it is much harder to arrest a large number of people falling at odd angles than it is for an individual person to arrest themselves. And of course if tragedy strikes and the entire group falls into the crevasse there is nobody left to coordinate a rescue. Effectively the chances of small failures has decreased slightly but the chances of catastrophic failures has gone way up.

I think of this example all the time in my work.

Most failures are totally unremarkable. We fix a bug. We slip a schedule. We change a feature. But sometimes there are catastrophic failures with long lasting consequences. And when we investigate those failures they are almost always the consequence of a chain of minor failures linked together in ways we often didn’t understand at the time.

It has always struck me that the more edifice you build to prevent minor failures the larger the capacity you create for catastrophic ones, just like climbers roped together on a mountaintop. Years later I finally stumbled upon a formal framing of this phenomena in a paper from the University of Chicago titled “How Complex Systems Fail.” It was ostensibly written for the medical community but the lessons it contains are universal. One particularly salient observation is that we value the speed and production of these complex systems which push us towards greater risk until a failure pushes us the other way. Humans are both the greatest threat and the greatest opportunity for stability.

I am not suggesting we stop trying to prevent failures. Indeed there are well known counterexamples worth considering. Air travel has gotten almost monotonically safer over time. However I do think one reason for that is the stability of the underlying systems, as air travel hasn’t significantly changed in almost 60 years. The pressure I mention above to increase output has been balanced not just through effective regulation but also economics.

Cars have also gotten safer though that story is more complicated than it seems. When seat belts became legally required the number of fatalities went down meaningfully. But the number of accidents and injuries actually went up. People felt safer and as a consequence took more risk. That’s almost certainly a good trade but it does speak to the degree to which humans adjust their activities relative to risk which makes it hard for failure to be eliminated.

My concern is that many of the efforts we have to defend against failure create catastrophic complexity without meaningfully reducing failure at all. For example after a rare failure we may introduce daily complexity in spite of the fact that failure was already acknowledged to be rare. I recall the story of the nuclear meltdown at 3 Mile Island where a sensor was installed to detect a rare but serious condition. Unfortunately the nature of the condition made it impossible for the sensor to be very reliable but the engineers figured better to have false positives than miss the condition. But that backfired because the operators became habituated to that signal being faulty so they ignored it when it wasn’t. Had no sensor been installed at all it is very likely they would have noticed other conditions precipitating the disaster and prevented it.

This is the reason why I tend to prefer less structure in organizations. There is more chaos but failures tend to be less correlated and less catastrophic. Instead of protecting my teams from change I try to ensure they are antifragile. Instead of preventing all mistakes I focus more on preventing a small number of major mistakes. Instead of enforcing stronger processes I try to give more latitude to people on the ground.

This is a post I expect to refer back to quite a bit in the future at times when I propose a high level framework which begs for more specific detail to operationalize. While I never intend to be vague I do prefer leaving the last mile of work to those closer to the work who have more visibility into how it impacts them.