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More information is usually considered "better". Let's say a rational agent chooses optimally given his information on the circumstances of a particular decision problem. Then providing him with more or better information makes him (weakly) better off.

Other agents might be made worse off in the process, and total welfare might even decrease. Danove et al. (2003) e.g. argue that the introduction of mandatory "report cards" in New York and Pennsylvania in the 1990ies to evaluate bypass surgeries reduced welfare because it incentivized doctors to avoid treating very old or sick patients. In this example all patients got more information, and some of them, but not all, ended up worse off.

But there are also circumstances where providing agents with more information makes everybody worse off. When visitors are about to leave a crowded theater, truthfully informing them that a fire just broke out behind the curtain might have disastrous consequences for all of them. Informing the public that a particular bank is in trouble could trigger a bank run that leaves everybody worse off.

What are other such phenomena? I am looking for examples (in theoretical models or in the real world) of the latter kind, where exogenously providing a group of agents with more or better information leads to a new equilibrium which is Pareto inferior compared to the old one.

VARulle
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    See also "Reverse Tinkerbell Effect" – CodyBugstein Feb 24 '20 at 22:12
  • Does this information need to be objectively true? I can list a lot of cases, when floods of lies can be disadvantageous. – Nyos Feb 25 '20 at 12:34
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    @Nyos: Yes, in my understanding "information" is by definition true, otherwise I'd rather call it disinformation. – VARulle Feb 25 '20 at 13:41
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    @VARulle The two cases that you mentioned are not fulfilling your criteria: in a theater fire there are potentially people that are better off, those who didn't fall victims to the stampede and managed to exit because of the alarm. In case of a bank run most people are worse off, but not the first ones who withdraw their full balance. – user3819867 Feb 25 '20 at 17:04
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    I don't have enough reputation for an answer, so leaving this as a comment. How about an old marriage? Both parties have occasional thoughts that they might be happier with someone else (because they're human and we all have these thoughts), but are happier together than they would be if they divorced. But if they each knew how often their partner had occasional stray thoughts, they might end up agreeing to a divorce, leaving them both worse off. – CPomerantz Feb 25 '20 at 21:26
  • @CPomerantz: You need reputation to answer questions? I thought it is the other way round... As for your answer, thx--this is an interesting example, since here ins some sense your utility depends directly on your knowledge. – VARulle Feb 26 '20 at 08:38
  • @user3819867: I don't think that just escaping the stampede makes you strictly better off compared to leaving the theater quietly--at the very least you will have to run, which is costly. It's similar for the bank run example. – VARulle Feb 26 '20 at 08:59
  • @VARulle If people are not told there is a fire, why would they leave? – user3819867 Feb 26 '20 at 12:21
  • More generally beyond the theatre example it's any information that induces mass panic, such as knowing the full detail about any/ every asteroid heading towards Earth right now, the extent of spies within your community (i.e. if it turned out you live in a society like East Berlin with spies everywhere you'd be a lot more isolated), etc. Similarly knowing what people voted for in an election can result in potential avenues for bribery and therefore more corruption in the democratic process. – Luke Briggs Feb 26 '20 at 13:25
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    @VARulle I have 100 rep because I have enough rep on other Stack Exchange sites. But you need 10 rep earned on this Stack Exchange to answer because it's a "Highly Active Question". – CPomerantz Feb 26 '20 at 15:44
  • To whoever upvoted my comment, I appreciate it but it doesn't reward reputation. I will have to wait until the question is un-protected to write an answer. – CPomerantz Feb 26 '20 at 19:31
  • Here is an interesting somewhat-fantasy-like story about a few pieces of "information" (statements) that could basically destroy the world, so not knowing of their existence is better for everyone: https://slatestarcodex.com/2018/10/30/sort-by-controversial/ – Fabian Röling Feb 26 '20 at 20:58
  • @user3819867, because the show is over. That's why I wrote "... are about to leave ...". – VARulle Feb 27 '20 at 08:58
  • I suppose that "mandatory report cards" refers to health care ratings? In that case the information released is misleading. Complete information in a "hospital report card" would include who had surgery there and would be normalized by patient risk. – Peter - Reinstate Monica Feb 27 '20 at 16:09
  • You can always control people by controlling which pieces of information you share. If I tell you A, D and F, you might be worse off than if I didn't tell you anything; but if you learn B, C and E, you will be better off overall. Does this count as "more information is worse" or "more information is better"? :) One solution to information being harmful is restricting access to the information; another is providing even more information. The former is probably warranted sometimes ("how to build a nuke at home in seven easy steps") :) Would the latter count for your question or not? – Luaan Feb 28 '20 at 07:38
  • @Luaan, probably not. An agent building a nuke at home would benefit from doing so (by revealed preference), unless you assume that he is irrational or misinformed to begin with. But then there are many trivial such examples even in single-agent decision problems, which is not that interesting. – VARulle Feb 28 '20 at 08:55
  • The question is still protected, so I still can't answer, but I came across another interesting example in daily life recently. It's similar to my previous comment answer in that it deals with interpersonal relations, but this actually happened in real life. Two (American) friends, one is a Republican the other is a Democrat. As long as they don't know that, their friendship is great. As soon as they start talking about politics and discover their political difference, they start constantly arguing and the friendship falls apart, leaving them both worse off. – CPomerantz Mar 05 '20 at 19:17

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Traffic reports are another type of information that potentially makes everyone worse off.

A recent working paper (Wiseman and Wiseman 2019, https://drive.google.com/open?id=10B6VudYJOQB5w2UVBrYEjYc5wwzGZc8Z) shows this in a simple model of traffic.

I quote from the paper, "...public information about road conditions tends to increase average travel time when...3) the scale of the traffic network is large." This corresponds to their Theorem 3, where "...in a scaled-up version of any environment with excess capacity, traffic reports increase expected travel time."

Yet another broad way of thinking about your question is in terms of monitoring structures of repeated games. A recent paper (Sugaya and Wolitzky 2018 JPE, http://economics.mit.edu/files/11455) look at imperfect monitoring in cartels and show that less transparency can facilitate collusion, making all participants better off.

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    This is a good one. I recall an article (not sure where, now) making this case about map applications that give near-real-time traffic re-routing in response to conditions. Although, the argument there is that the larger pool of information is segmented - Google Maps doesn't know where iPhones are sending their users, and vice-versa, and of course cities have no idea what either service is doing. – heh Feb 24 '20 at 15:44
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    Another way of thinking about this is that "how bad" it is to be late might not scale linearly with the lateness. It's easy to imagine that there might be a step change in badness when you're late at all. So it's worse, on the whole, for everyone to be 1 minute late than it is for 1 person in 15 to be 15 minutes late. Real time traffic reports that "level out" traffic might make more people a little bit late, even if average travel time were the same or reduced. – StackOverthrow Feb 24 '20 at 22:24
  • I think traffic information making everyone worse off is a candidate for @Luaan's concept of being more, but insufficient. The everyone worse off here is typically a result of alternative routes with smaller capacity (otherwise there would be the primary, not the alternative) exceeding their capacity. But the outcome may change to everyone better off if you can give sufficient information to just approach but not exceed that capacity ("cars with license plate ending in 1, 2 or 3 please take detour A") 2) these "everyone worse off" thoughts do not consider that some who are in a traffic jam
  • – cbeleites unhappy with SX Mar 01 '20 at 15:46
  • ... (and the ones waiting for them) are better off already if the information allows them to call that they will be aproximately xxx min late. – cbeleites unhappy with SX Mar 01 '20 at 15:48