Survival bias: what is this logical error?

Sometimes we draw overly optimistic conclusions about a particular problem and we do it. through survival.

We will discover the implications of this logical error and some of the most common scenarios in which we can observe this phenomenon, as we will see that it is not a bias that has greater prevalence in a given area but can occur in a given area. variety of situations.

    What is survival bias?

    Survival bias or survivor bias is a kind of failure of logical argumentation that leads us to focus only on the elements that have passed a certain selection, Ignoring, on the other hand, all those who have not overcome it. This limitation can lead the observer to completely ignore the mere existence of all of these elements, which can sometimes become a majority or have interesting attributes that have been lost in oblivion.

    It is not just this error. In addition, survival bias can sometimes lead us to fall into unwarranted optimism. And it is this to assess a certain situation by taking into account only those persons or elements who have passed the evaluation barrier or the selection process in question. Relying only on the characteristics or testimonials of these and not on the total number of participants can be a mistake.

    To be able to better understand what survival bias is we will try to visualize it with an example. Suppose we organize a car race and when it ends we take it for granted that the top three are arguably the best cars to compete in. But a lot of things happened that left the other cars behind.

    For example, an accident may have occurred which left first class cars inoperable. Perhaps the tires chosen by some of the participants were not the best to take advantage of the characteristics of the car and the circuit. They may even have been worse drivers and failed to tap the potential of the vehicle, which could have even been better than that of the winners.

    These are just a few of the options we could easily fall for survival bias, thinking cars in the first place are, automatically, the best. To arrive at this affirmation, we must study in depth the characteristics, not only of them, but also of all the other participants. Only then will we be able to draw conclusions correctly.

    Areas in which this logical error appears a lot

    Survival bias is a phenomenon that can occur in virtually any field. This is why we are going to make a compilation of some of them and thus be able to understand the extent of this logical error and the dangers it entails if we are not aware of its effects.

    1. At the economic level

    One of the most important scenarios for considering the possible occurrence of poor survival is probably economic or financial, as the consequences can be dire. In this case, this bias would refer to the exclusion in any type of report of all businesses or other types of organizations that have been closed.

    Therefore, information relating to a multitude of businesses that after a failure would not be added to certain statistics and indicators, which would only consist of those who are still standing, would be left out. This would be one of those cases where a lot of information is overlooked, sometimes very important.

    2. At the historical level

    We’ve all heard the claim that history is written by winners. In a way, it is a way of expressing the effect of survival bias on historical events. In these cases, for example, Usually, the victorious side of the conflict is tasked with shaping the history of the war they fought for, its origins and consequences..

    Sometimes this story is reasonably objective, but in others it is a real headache for historians, who must study the documents in detail to ensure that the facts happened as this part argues. Assuming there are still documents to be investigated, such as irrelevant evidence can also be suppressed, about a past that “never” happened.

    3. In the professional field

    We must not forget that the survival bias also applies to people themselves and of course to their careers. For every great footballer, famous actor, famous writer or prestigious manager, there are thousands who, having similar characteristics, have failed on this same path.

    In that case, to consider only the qualities of those who have succeeded as an infallible formula would be a mistakeAs we would leave out a multitude of variables, many of which are uncontrollable or random, which surely have a lot to say in the failure of others.

    4. In the quality of the goods

    Sometimes we have the feeling that the objects, clothes or machines created today are deliberately designed to last for a certain period of time. They call it planned obsolescence. The argument is that there are elements of the same kind but created a long time ago which still retain their qualities.

    This would be a case of survival bias, as we would focus on the concrete example and ignore the immense amount of similar material that has never come to light today. If we took into account the total number of objects created at any one time and could come up with a statistic on which have proven to be durable and which have not, maybe our opinion would change.

    Surely we would realize that in fact, only products designed with very specific characteristics lasted longer than usual and on the contrary, there have been multitudes who could not withstand the passage of time as well as these minority cases.

      5. In terms of architecture

      The reader will surely get the well-founded impression that older buildings tend to look much better than modern ones. Does this mean that absolutely all the constructions that were made in the past were majestic and more extremely resistant? Absolutely not. It would certainly come under the survival bias.

      How then to explain that all (or almost all) the old buildings preserved in the cities are remarkably more beautiful than the more recent ones? Due to the constant renewal processes that cities undergo every few decades. This causes most buildings to have an expiration date, with the exception of those which are particularly notable for their features.

      Therefore, these tend to be heritage and it is about restoring them as much as possible instead of tearing them down and replacing them with others. This is the cause of the low survival rate, as it suggests that only ancient buildings survive, regardless of the fact that for all that has come to our time there are hundreds that have been reduced to rubble.

      6. In war strategies

      One of the strategies pursued by the US military during World War II was to study the impacts of bullets received by its bombers during air battles, in order to protect in particular the areas where most of the fire was observed. It seemed like a brilliant strategy, but one key factor was overlooked: all downed planes in combat.

      The fact of not being able to study the destroyed plane, made it possible to sign where they received the blows precisely those which suffered the most serious damage. So this is a clear case of survival bias.

      7. The seven lives of cats

      Who doesn’t know the popular saying that cats have seven lives? One of the tests typically performed to support this claim is that cats generally survive falls from great heights. How do you know that? Because veterinarians typically treat specimens of those animals that have suffered injuries from a fall of several floors.

      But this is another case of survival bias, as we are only evaluating cases of cats who survived falls, leaving out all cases of cats who, unfortunately, are not so fortunate and die from the consequences. of precipitation in a vacuum. Probably with the latter number being larger, but being ignored by statistics, we still believe cats have seven lives.

      Bibliographical references:

      • Brown, SJ, Goetzmann, W., Ibbotson, RG, Ross, SA (1992). Survival bias in performance studies. The review of financial studies.
      • Mangel, M., Samaniego, F. (1984). Abraham Wald’s work on aircraft survival. Journal of the American Statistical Association.
      • Shermer, M. (2014). How the survivor bias distorts reality. American scientist.
      • Whitney, WO, Mehlhaff, CJ (1987). High altitude syndrome in cats. Journal of the American Veterinary Medical Association.

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