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I joined SO when there were are 150K questions. Now there are some 330K questions.

It appears that the number of visits to questions, and the real longevity of an interesting question, appear (IMHO, no empirical data) rapidly dropping off. This seems a like a natural consequence: with floods of new questions coming in, older questions simply disappear in an avalanche.

Disk caches have the same problem in operating systems. If the number of queries that mention cache elements is high enough, the cache elements tend to stay in the cache. If the number of queries for new things exceeds the cache size, the cache gets filled with new items and there's never any cache hits.

So what are the properties of SO as the number of questions goes to infinity? (Or 10 million, that's only 1 question per programmer on the planet and I'm sure we all have at least one)? What properties of the design of SO provides any assurance that it won't die by simply being drowned?

EDIT Aug 7 2011: Now SO has some 1.9 million questions. I go for several days at a time now when no interesting questions come up, in spite of the probably much larger volume of users that exist compared to when I asked the question. Jon Skeet below vaguely answered my original post, but didn't back up with facts. So... I repeat the question... what designed-in properties does SO have to prevent it from getting drowned?

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there's only 10,000,000 programmers on earth? That's only ~1:1000 people. I would expect it to be higher - especially when considering hobbyists – warren Oct 8 '09 at 10:31
@Rich B The title just sounds wrong right now. – alex Oct 8 '09 at 13:41
@warren: how many programmers you know outside your circle of friends/coworkers? How many people are there in a common IT company compared to the amount of programmers in the same company? 1:1000 seems optimistic to me. – perbert Oct 8 '09 at 13:54
@Rich: I think your title change lost the essence of the question. I've revised to be closer inline with what I thought was the point. – Ira Baxter Oct 8 '09 at 14:08
@Ira Baxter much better! Thanks! – alex Oct 8 '09 at 14:34
@warren: if you include hobbyists, then the number is likely much bigger than 10 million. All this does is reinforce the argument. – Ira Baxter Oct 8 '09 at 14:46

The rate at which questions are being asked doesn't seem to have grown exponentially, which would be the worrying thing IMO. Indeed, as SO gains more and more questions, there will be more and more "cache hits" when someone goes to ask a question to start with.

(There are graphs of this somewhere - I'll look for them in a minute.)

To my mind it's still working - if I've been away for a few hours, most of the recent-ish questions I look at seem to have good answers. There's a problem in terms of keeping old questions up-to-date (as new technologies arrive which solve them in a different way) but I think that's due to time rather than question volume.

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It isn't exponential growth rates that kill you. It is the mean distance between the questions you see, and the questions you care about. Once that gap gets large enough, everything looks like noise and you stop caring. And the older questions/answers, which is where one hopes the value is cached, get correspondingly hard to find. If one believes that there's an infinite variety of questions, I don't see how you avoid this. If the variety isn't infinite, some way to cull the redundant ones needs to be found. – Ira Baxter Oct 8 '09 at 14:11
(May 10, 2010) I never did see those graphs. Now we're up to 650,000 questions. – Ira Baxter May 11 '10 at 0:56
@Ira: No, I don't think I found them. Still, questions still seem to get answered... – Jon Skeet May 11 '10 at 3:59
true, lots seem to get answered. But I'm personally beginning to see exactly the phenomenon I suggested two comments above this: a couple of days go by before I see a question I care about, even fishing with tags. And (gut feel), many of the questions in the top 10 pages of questions seem to have scores like 0/0 or 0/1. It would be interesting to see graphs of score rate change vs age on recent questions, vs. the same on older questions. – Ira Baxter May 15 '10 at 7:08
Erm. Fewer questions get asked, because more questions have already been answered? I mean, we get enough basics that get asked over and over again. We treat them with the 'close-as-duplicate' flag. For a reason. The drop-off is by design. – sehe Sep 4 '12 at 21:42

The faster questions are asked, the less likely yours is to be answered. People ten take a new approach to solving the problem and go elsewhere - one question I saw 4 hours ago still only has 7 views, and no answers - I'd suggest the longer it remains unanswered, the less the chance it will be answered.

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Then again, it allows for hunters to have time without scrambling to be FGITW and well thought-out in their answers. – random Oct 8 '09 at 16:20
Maybe; the problem seems to be worse on SU than SO – Rowland Shaw Oct 8 '09 at 20:05

Well, the growth of SO really means that users need to find specific tags that they're interested in.

The homepage already changed as documented here:

I’ll be honest with you, this change makes me nervous. It’s like Colonel Sanders mucking around with his magical blend of 11 herbs and spices. But at the same time, the old simple “questions by activity date” homepage default was clearly not working with the 2,000+ questions being asked on Stack Overflow each and every day. Something had to change.

(Up to 4k questions/day now.)

Also we are getting much, much stricter in the questions will will allow from new users, and we are aggressively blocking the ones we don't feel meet our quality standards.

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by the clever(er) use of labels to filter off the noise. I personally only look at my interested labels, and ignore any other questions.

i m sure if the community moderates the bad seeds out (bad seeds being users that post poorly), stackoverflow will continue to be a valuable resource.

what i am concerned about is the fact that is coming into existance. Stackoverflow is not a good platform for CV intelligence gathering. It is not something you use to get a job. If you happen to chance upon a job because the employer found you on SO, then good. But dont make SO a place to pad out my resume - it is a computing and programming resource first and foremost. What i fear is that if i dont perform well on SO, i will be looked down upon from the employer's perspective - that ought to never happen.

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…Then don't put up a profile on CSO? – Josh Hunt Oct 8 '09 at 10:43
I really haven't found a good way to make filtering work for me. Some of the things I'm interested in just have too many possible tags. And the way it emphasizes and de-emphasizes based on selected tags is more annoying than helpful. I really don't visit much anymore because it's too busy (stuff falls off the screen too fast). When I do visit, I'm just searching for some particular item, I don't scan through the list of new things anymore. No solutions here, just a description of what's happening. Maybe that'll help someone else come up with a solution! – Brian Knoblauch Oct 8 '09 at 11:33
@Chii: Back up your assertion that SO is not a good platform for CVs. Many, many folks here on SO answer questions very specifically to demonstrate their prowess to potential employers, to expand their online tech persona. Just because you may not measure up is not good enough. It almost sounds like you are scared of competition and would like to hide behind smoke-n-mirrors (aka standardized HR tests and copious use of buzz words on your CV.) – Stu Thompson Oct 8 '09 at 12:32
btw: -1 (yada yada yada) – Stu Thompson Oct 8 '09 at 12:33
@stu: i dont need to assert anything about SO being good or bad, i m jsut saying that i dont like it if it becomes a defacto method for a clueless employer to judge the quality of a candidate. The problem with what you are saying is that, you assume being able to answer questions for some online cred equates to being a good employee. An employer should be able to filter out the bad ones, using something like a probation method, not some online profile ala facebook. that is why i dont connect my online persona with my offline ones. – Chii Oct 25 '09 at 8:38
@joshhunt: i dont plan to put anything up on CSO - but i may be forced to, like i was forced to join facebook because my friends were using them to organize events. – Chii Oct 25 '09 at 8:42

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