Many people claim that the millenium bug (Y2K)was an unnecessary panic. The argument goes: "On Jan 2000, there were only a few problems attributable to the Y2K problem. Therefore the effort used to solve it were wasted."

As one of those who actually removed a Y2K bug, I know this statement is untrue.

A more detailed example is: "Companies who did nothing about the Y2K bug did not suffer any problems. Therefore effort to remove bugs were wasted".

The truth is that big software suppliers solved the problems; their customers did not need to do anything other than accept the routine updates which delivered the fixed software. So it is strue that many companies did nothing and suffered no problems, but it is not true that effort was wasted.

Is there a specific fallacy that describes falsely concluding that an activity was unnecessary because the activity successfully removed the evidence that it was effective?

  • Great question. I am reminded of this statement...we can fire the security guard because we had no thefts this year.
    – Gordon
    Jan 20, 2018 at 14:46
  • Just fyi/clarification, I also had several y2k remediation contracts in 1999. Most were pretty trivial fixes, although a few required some substantial code/database redesign. And the fallacy was the mistaken public warning that many would require substantial redesign, and that a good number of those wouldn't be completed on schedule (before 1/1/00). So the "panic" aspect was definitely pretty unnecessary. But few, if any, fallaciously suggested that the necessary remediation was unwarranted.
    – user19423
    Jan 21, 2018 at 3:45
  • Not an answer but there were a plenty of companies (mine included) that spent a lot of money on upgrades etc, knowing full well that they would have, provably, no material effect. They did it because, if there was an issue, they could say that they had taken it seriously. It's not a fallacy but it does have it's own, pithy, phrase: "no-one is fired for buying IBM"
    – Alex
    Mar 16, 2018 at 18:46

2 Answers 2


I don't think there's a named fallacy for this. But it seems to be a case of : 'no perceived effect, therefore no cause'. Or 'no perception of problem, therefore no problem'.

  • 1
    I agree. It may be best to classify the error as simple ignorance. Your word "perceived" is key. The problem is that neither the reality of the problem nor the real benefit from the work done, were perceived. People then feel entitled to assume that the work was wasted. The Y2K problem was presented in public as doom about to befall us. Behind the scenes, it was known that real harm would befall many vital systems unless a lot of corrective work was done. Jan 20, 2018 at 18:46
  • @Peter Jordan. Thanks for comment. You've told me a lot more than I knew about Y2K - appreciated. Best - Geoff
    – Geoffrey Thomas
    Jan 20, 2018 at 20:25

The line of thought mentioned above is most likely an inverse (if a then b --> if not a then not b) version of the Post Hoc Ergo Propter Hoc fallacy.

The fallacy is of the form:

Because event Y followed event X, event X must have caused event Y.

To think critically, one has to be careful not to jump to a conclusion about something merely based on the sequence and timing of such events. Such is the case with the post hoc ergo propter hoc fallacy.

The speaker has said that because there were few problems (event Y) that followed Y2K (event X), therefore Y2K must not have caused problems.

An identical version of the post hoc ergo propter hoc would have been like:

Because numerous computer problems followed Y2K, Y2K must have caused them.

The speaker has jumped to a conclusion and made a hasty generalization--which in this case is the inverse! (because blank Y did not follow blank X then blank X must not have caused blank Y)

The speaker has also ignored that there were many people working around the clock to make sure such bugs would be fixed if presented; this may the real reason why few problems presented after Y2K, not that Y2K itself had no effect.

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