As provable by Question Number 1 the site started to exist almost exactly six years ago.

Everybody who feels like saying something on this occasion, feel free to post an answer.

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    $\begingroup$ If we take the posting of Question Number 1 as a basis, the posting of this comment marks a little more precisely the 6th anniversary of MathOverflow! $\endgroup$
    – Stefan Kohl Mod
    Sep 28, 2015 at 16:11
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    $\begingroup$ Precise to the second! That's impressive. $\endgroup$
    – user9072
    Sep 28, 2015 at 16:21
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    $\begingroup$ The fifth anniversary was a disturbingly short time ago. Gerhard "Zoom Goes The Time! Zoom!" Paseman, 2015.09.28 $\endgroup$ Sep 28, 2015 at 19:42
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    $\begingroup$ @GerhardPaseman See my answer for an explanation :D $\endgroup$ Sep 30, 2015 at 5:12
  • $\begingroup$ Many of our users are not native speakers of English ... as illustrated by the title "MO exists since six years". $\endgroup$ Jun 29, 2018 at 13:25

2 Answers 2


Happy birthday MO! While we're enjoying all this free cake, maybe we can take a moment to reflect on how (or even whether) MO has grown in the past year.

Out of curiosity, I put together some search links that show the most highly voted questions and answers in each of MO's 6 years of existence.

In parentheses, I include:

(the number of Q or A posted that year with score at least 1 / the total number of Q or A for that year)

(for some reason it seems to be harder to search for posts with score at least 0). These were taken from the numbers of search results, which should be fairly close to the true number of non-deleted Q's or A's.

  • Year 6: Q (9250/11257), A (10812/11964)
  • Year 5: Q (9633/10877), A (12340/13336)
  • Year 4: Q (9967/11394), A (14549/15682) (migration to MO 2.0, on 2013-06-24)
  • Year 3: Q (9328/10340), A (14965/16167)
  • Year 2: Q (9864/10778), A (19467/20850)
  • Year 1: Q (9401/10001), A (24610/26210)

It's interesting that the number of posted answers seems to be decreasing. At least some of this effect is due to the fact that "big list" questions are no longer as frequently posted or accepted on the site (a good thing, I think).

However, the fraction of questions and answers with score at least 1 seems to be significantly lower in year 6 than in previous years. The absolute number is also a bit lower.

By popular request, the above searches and numbers with CW posts filtered out:

  • Year 6: Q (9138/11115), A (9793/10796)
  • Year 5: Q (9501/10738), A (11157/12030)
  • Year 4: Q (9718/11128), A (12951/13971) (migration to MO 2.0, on 2013-06-24)
  • Year 3: Q (9030/10034), A (12910/13946)
  • Year 2: Q (9393/10288), A (15582/16690)
  • Year 1: Q (8696/9278), A (18643/19946)

The fraction of CW posts does seem to have been significantly larger in the early years of MO, though it doesn't fully explain the decrease in the average number of answers per question.

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    $\begingroup$ To search for posts with score at least 0 use score:0.. as a search parameter. $\endgroup$
    – user642796
    Sep 29, 2015 at 2:37
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    $\begingroup$ Many of the very popular questions and answers are of "big list" type, usually CW. Would it be possible to compile a similar list, but excluding CW questions? (Mere curiosity as well!) $\endgroup$
    – Wolfgang
    Sep 29, 2015 at 19:35

A good evidence for me that Mathematics is free of time - although I'm here for almost two years by now, it feels at the same time like my interactions here happened all at the same moment and like I've been here always :D


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