As I've been using Mathematics, I've noticed that questions related to statistics or probabilities take more time to get answered, if they get answered, than at CV. This is just my impression without any evidence to support it. (I may be wrong about this.) So, I've cross-posted sometimes. Yes, mea culpa, mea culpa, mea maxima culpa...

Recently I was warned not to do it. Hence my two-part question:

  1. Why should we not cross-post? (Any link or help with this information is very welcome.)
  2. What are the possible consequences of persisting in this behaviour?

Any help would be appreciated.

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    $\begingroup$ (1) What is "ME"? (2) Concerning cross-posting, please see meta.stats.stackexchange.com/questions/2031. $\endgroup$
    – whuber Mod
    Jul 30, 2014 at 16:26
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    $\begingroup$ It's Mathematics. ;) $\endgroup$ Jul 30, 2014 at 23:09
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    $\begingroup$ Regarding "time-to-respond", at least for probability theory and mathematical statistics questions, I would say the opposite happens: the answering team never sleeps over there. $\endgroup$ Aug 1, 2014 at 21:20
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    $\begingroup$ I would say my experience doesn't match yours. I go there (math.SE) sometimes to answer some stats or prob questions and generally find the ones that have posted in say the last day that I'd be interested in looking at (which mostly means 'I am competent to respond to') all have answers. This is rarely the case here, where I can usually find 4 or 5 in the new queue that I'd happily answer, and which are either unanswered or where I think I can contribute something useful anyway. If I can find one on math.SE that's not answered, it usually has an answer before I finish typing. $\endgroup$
    – Glen_b
    Aug 5, 2014 at 5:20
  • $\begingroup$ @Glen_b, yes it seems that you're right. By the way, why then is there a stat.stack outside mathematics? Wouldn't it be better to just join both? $\endgroup$ Aug 5, 2014 at 9:43
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    $\begingroup$ (1) not every statistical question is particularly a mathematical question, and even when it is, there seems to be a tendency for many (though not all) mathematicians to focus only on very particular aspects of it for some reason; (2) the style of answers (and the overall culture) tends to be quite different at the two sites. I don't think that the most common approaches taken there tend to suit a large fraction of the people who ask here, though there is an overlap for particular kinds of question. There are questions here that I think would be likely to close or go unanswered there. $\endgroup$
    – Glen_b
    Aug 5, 2014 at 10:24
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    $\begingroup$ @Glen_b And aren't many questions left unanswered a pointer to this community needing more experts/knowledgeable users such as you? $\endgroup$ Aug 5, 2014 at 14:14
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    $\begingroup$ @Anoldmaninthesea. No doubt more statisticians actively answering questions here would be helpful for getting more questions answered, though I don't think it's the only factor. As I mentioned, the kind of question tends to be different, for example; I think it's an issue with a variety of causes. $\endgroup$
    – Glen_b
    Aug 5, 2014 at 21:11
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    $\begingroup$ related mathematics-vs-cross-validated $\endgroup$
    – TooTone
    Aug 10, 2014 at 18:27

3 Answers 3



  1. Your culpa doesn't seem maxima enough! Knowingly cross-posting...Shame!!

  2. I'm guessing you're responding to this comment on your recent Mathematics question. Do clarify if your ME $\ne$ Mathematics. We may wish to discuss the issue on a per-sister-site basis, and having it arise WRT a different site than usual could make this question unique. As is, it might be a dupe of "Cross-posting in CV and math.SE tends to become an epidemic", but it can't be closed as such for lack of an upvoted answer over there. I also like that you've emphasized the why-nots and what-ifs over the what-should-we-do-abouts; I have much more to say about these. BTW, your question also reincarnates an upvoted comment on that question, so let's have at it.


The more I look into this cross-posting issue is the more it seems controversial to me, rather than clear-cut like the help page suggests:

Please note, however, that cross-posting is not encouraged on SE sites. Choose one best location to post your question. Later, if it proves better suited on another site, it can be migrated.

On that side of the fence, there's also a big fat $\mathbf{NO}$ sitting atop the accepted answer to the , "Is cross-posting a question on multiple Stack Exchange sites permitted if the question is on-topic for each site?" Further down, the second-most upvoted answer is a slippery slope argument against cross-posts by SE's own Jeff Atwood (self-appointed Stack Overflow Valued Associate #00001). Here on CV, our very own mbq♦ even posted the biggest "NO" you'll find on the network! Looks clear-cut, no?

Well...no – look a little further. On the above questions, highly upvoted comments challenge both the objectivity of the accepted answer and the slipperiness of the slope. Below, two newer answers argue that there are exceptions and good practices for them, and there are systemic incentives. The former has a supportive comment from Jeff that draws a clearer line between bad and good (or at least acceptable) cross-posting; it has plenty of upvotes too. The latter answer was brief and rather unconvincing (which is an ill-fated approach to arguing against dominant opinion), but it has my upvote – there certainly are wide disparities in site traffic, and I've now edited in a graph to demonstrate just how wide and provided supporting arguments. These include mention of a worthy on MSE with comments linking many others, and a similar suggestion for good cross-posting practices made by Shog9 (a SE Community Manager and kind of a big deal on MSE, second only to Jeff there). Internally, Robert Cartaino (Director of Community Development and Valued Associate #00005) has also been around longer, and he has also supported cross-posting in "edge cases", which I think are losing their "edge" as the network grows and more sites overlap more naturally. On yet another popular feature request, another MSE OG Robert Harvey echoes the conditional and informal nature of cross-posting policy. CV also expresses dissent on the topic: "Is the help 'misinformed' on the question of cross-posting?"

Hence I wonder if the illusion of clear-cut policy isn't a relic of Jeff's original design that is obsolescing as the network grows in ways that were unforeseeable when these matters were "decided"...

My answer

1) Why should we not cross-post?

Because you're probably going to do it wrong if you haven't thought it through (see background links). That being said, there is a way to cross-post conscientiously for questions that deserve it:

  1. Read your target sites' on-topic help pages to check if your question is on-topic at each.
  2. Search the sites' meta-questions for issues with your question's specific topic (think at the level of specificity that decides what tags to use) and issues of overlap with the other site's main domain. You'll not often be the first to want to cross-post on your particular pair of target sites.
  3. Do not copy-paste; reframe your question. Differentiate your two posts to emphasize what aspect(s) of your question you want each community to weigh in on separately. Don't just cross-post to enlarge your audience; do it because each audience may have a different perspective on your problem, and do your part to encourage a different angle of approach on each site.
  4. Link to your other version of the question on the other site. This facilitates the good side of cross-posting: open juxtaposition of different sets of answers and a bridge between related communities. It also indicates that you're not just thinking of yourself and trying to circumvent the dominant policy thoughtlessly or surreptitiously. Don't underestimate the power of ruffled feathers; tread lightly and respond diplomatically to any critiques from the local leaders. Don't overreact.

2) What are the possible consequences of persisting in this behaviour?

This doesn't seem to come up much, which is probably a good thing! I suspect people tend to settle on one site or another depending on which gives the better (or worse) reception, and maybe individuals really don't have that many "edge cases" to offer. I think the collective behavior of the communities persists more, in that new users keep arriving without site preferences, nuanced understanding of sites' topic boundaries, or awareness of the dominant anti-cross-posting policy. This probably fuels that policy's power, because new users tend to ask worse questions anyway*. Hence they probably also take the brunt of that policy's force, for better or worse. They receive more negative feedback at first (call it hazing if you will, but it's purposeful, and ideally, constructive), have more questions closed, and probably suffer a higher incidence of question bans. I think it must be very rare for people to achieve that level of rejection for cross-posting alone though; truly bad cross-posting is probably comorbid with many other troublesome behaviors that compound to produce that end result.

I suppose if you've "gotten away with it" before, someone might recognize that you're at it again and respond more bluntly or develop an attitude toward you, but it's far wiser to worry about the community's opinion than an individual's. Bringing the issue to the per-site metas (or having it brought there, maybe even in a way that's stilted against you, though we're supposed to keep it impersonal) is the upside of persistence. This is a touchy issue regarding which the whole network needs to work out its ambivalence and resolve its differences. There may be no complete, network-wide solution until a particularly ingenious feature request gets implemented (which could still be a long time from now – it's not gonna be easy), but in the meantime, individual communities can develop local policies and partnerships with their relatives. This is also where we decide what sites to list as migration paths within the flag / close-vote popup dialog. Popular cross-post pairings help inform that decision, because migration is another, softer solution for handling cross-posts that a site doesn't want to keep.

Thus if you feel compelled to persist, bring it up in meta! As you demonstrate, this is one good effect. Of course, if you follow step 2 above, you may also find that others have beaten you to it. Don't forget to vote while you're there! That's ultimately how we steer this thing (to the extent that we do ;).

* New users asking worse questions, IMO (as a newly badge-holding "steward"!), is due to natural ignorance of many SE policies, the effect of negative feedback from the community that shoos away bad attitudes and incoherent writers early on, and the positive effects of practice for those who persist. We don't just learn the site culture; we learn to communicate! IMO, the effects of this network's feedback are what make it special, and its culture worth accommodating.

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    $\begingroup$ Your answer has really been very informative and complete. I like your pedagogical perspective.It took me a bit to read most of the links, but most of them were very elucidative, like Robert Cartaino's answer. I'll start to, if the need arises, to only cross-post conscientiously, accordingly to your balanced and sound advices. :) I must say I was a bit fearful for the possible penalty I could have received, and also for being an action very frowned upon. I'm a bit more relaxed now, and also more conscientious on how to behave in that situation. $\endgroup$ Jul 30, 2014 at 23:25
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    $\begingroup$ Many thanks. And nice memes! =D $\endgroup$ Jul 30, 2014 at 23:38
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    $\begingroup$ +1 a comprehensive coverage of the issue. Congratulations on the Steward badge, that's a mighty effort. (If you want to make more progress on the Suggested Edit Steward-badge, you might have to leave more edits for lower rep users to be able to suggest, as difficult as that can be sometimes.) $\endgroup$
    – Glen_b
    Aug 1, 2014 at 1:27
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    $\begingroup$ Having developed those habits, I'm trying to transition away from basic curatorial tasks like editing, flagging, and first post reviews. After working on those for a while, I decided to use the gold badges as goalposts – a way of convincing myself that I'd done my part for the collective cause, learned what I could along the way, and that it's now time to focus on contributing in more self-directed, creative ways. Besides, though I've tried to be fastidious in editing & flagging, I'm no grammar nazi, and don't want to push my style or views too hard. Plenty of excuses for letting others do it! $\endgroup$ Aug 1, 2014 at 1:54
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    $\begingroup$ (+1) for the whole answer, and especially for policy 3) ("Do not copy-paste; reframe the question"). This is the single most convincing argument in favor of a productive cross-posting. $\endgroup$ Aug 1, 2014 at 22:09
  • $\begingroup$ @AlecosPapadopoulos: Yeah, that section you quote was the first thing I decided to bold, because that's the one behavior above all others that really seems to annoy people (and not without reason). After that, I decided I could bold some other stuff to improve skimmability, but I'd underline that one sentence too if I could. Arguably, alterations make it misfit the definition of a cross-post, in the same sense that small variations / paraphrasings are practically all one needs to do to avoid charges of plagiarism – a similar crime in that its egregiousness depends on exactness of the cloning $\endgroup$ Aug 1, 2014 at 22:25
  • $\begingroup$ +1, it's too bad we can't add bounties to meta threads ('one of the answers is exemplary and worthy of additional attention' ;-). $\endgroup$ Aug 3, 2014 at 23:46
  • $\begingroup$ Thanks :) Even setting personal gain aside, I agree it's too bad. Some feature requests about that: Bounty-like feature on metas and Can't post bounty on a per-site child meta $\endgroup$ Aug 4, 2014 at 0:38

A proposal: whenever we see questions over at math SE which clearly are more appropriate here, we should propose to move it here! (use the "flag" option and write that proposal, it is usually accepted). Especially when questions there did not already get good answers!

I try to do this agressively, that is also a way to make our site better known.


Trying to be a dutiful member of the community, I have previously alerted of accelerating cross-posting here, where I even posted a single-phrase update yesterday.

But this does not mean I disagree with the practice (or that I agree). Although Nick Stauner's answer is a tour-de-force, I have a few(...) things I would like to say on the matter:

Let a question that is on-topic on all sites that is cross-posted. Why should the practice be considered unethical or wasteful? These are the only two issues that one could raise against a cross-on-topic cross-posted question: either it wastes resources (time, attention, queue space etc) or it gives the asker an "unfair advantage". Or better, exactly because it creates an advantage by wasting resources, it should be considered unethical (me being an economist).

So, does it? Apparently yes. It appears on two different url's, it is read by different users... moreover, it may be answered in essentially the same way by two different persons, so even more waste...

But why is this a waste? Another important issue in Q&A sites is "why and who do we answer for?" In most cases, here and in other sites, the attitude is "we answer for the asker, but also for posting knowledge on the web for all future askers in need" (an attitude with which I agree). In that case, one could even argue that not cross-posting a cross-on-topic question is the attitude that should be considered unethical, since it deprives the other crowd of an interesting question that may receive a useful answer. And why is it a waste, if two different answerers provided the same answer? Answerers are doing it exclusively for their own psychological reward, so, each one separately was not hurt -on the contrary.

But, it is a waste for the community seen as a whole, because, the second answerer could have answered another question that now may have gone un-answered, making it an unfair situation for the asker that didn't get his answer...

But wait, what "community as a whole"? If the SE world was one community, why do we have many sites? The answer to that is rather obvious (practical, technical, socio-psychological reasons). But what if the SE word of websites was one integrated interface, where the existing Q&A sites where "thematic tags"? Would we then say "please don't tag each question with more than one thematic tag"? In other words, is there any essential difference between cross-posting a cross-on-topic question, and multi-taging a question?

These back-and-forth arguments can go on indefinitely. In other words, this is a classic case of a situation where either stance will to some degree violate some accepted principles and values, sometimes the same principle by a different route, a usual situation in human affairs. Cross-posting may be considered wasteful and unethical, but it can also be considered non-wasteful and ethical. Not-cross-posting may also be considered unethical...

In which case, we have to turn to "unintended consequences": what if cross-posting was accepted, even encouraged? Is there not a real probability that pretty soon, a visible number of users would start cross-posting even off-topic questions? Increasing many times the burden of each community to clean up the newly created mess, and then really causing a waste of resources?

To consider this probability as tangible, one should side with the opinion that humans may be controlled by ethical values, but they are driven by self-interest -and the Internet is notorious for lowering the power of the former (this is one of the things that I really like about CV by the way -it is so un-Internet from that perspective). I do side with this opinion, and so I consider this probability an important hurdle in embracing cross-posting. In a sense this is what Jeff Attwood advanced as a "slippery slope" argument in a more direct manner.

Cross-posting may have principled arguments in favor of it, especially as SE Q&A sites multiply and the degree of overlap increases. But my hunch is that the extend to which the practice will be mis-used, once it is openly allowed/encouraged, will outweigh the benefits from it.

Under this light, suggestions like Nick's "Don't copy-paste; Re-frame your question" are an excellent way to make productive and positive the "illegal" practice of cross-posting: "Give us a good reason to tolerate what you do, although we won't officially embrace it".

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    $\begingroup$ Alecos, if wasting other people time, or unknowingly consuming resources that could be used in other questions, can be avoided, at least in my opinion, by linking the two questions, and asking the answerer to post on both communities. If the users are already warned that the question is posted on both sites, then by answering on one, they would also answer on the other. If a tag is eventually created, it would be nice for it to do this automatically, without having to copy/paste ourselves. $\endgroup$ Aug 2, 2014 at 7:44

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