Is the bounty system effective?

Question

For years, people have been able to spend their hard-earned imaginary Internet points to add "bounties" to questions in order to attract more attention to them. (Because, really, "attention" is the only thing that you can be reasonably sure a bounty will give you.)

But does this extra attention translate into better results?

Granted, any individual question may not be really answerable or is still boring even with the extra carrot. And a question might be so interesting that it would have gotten a ton of (good) answers even without the bounty.

Do questions that have bounties get more/better answers—in aggregate—than questions that never had a bounty? Does this vary by site? If so, do bounties seem more effective at a certain site "size"?

Or is it really just a wash, and that all anyone ever gets for their bounty is extra attention?

Answer 1

The bounty system does bring more views to bountied questions. On average, Stack Overflow questions get 1455 views. Bountied questions average 2631. It stands to reason that the more people who see a question, the better the odds it will get a quality answer.

To test that, I divided all answers into three groups:

1. All answers whether their question has been bountied or not (the control),
2. Answers that arrived before the bounty (before), and
3. Answers that arrived after the bounty (after).

Since questions can have multiple bounties, an answer might belong to all three groups. A slightly cleaner test would only look at questions with just one bounty.

Score is our usual method of determining quality. The query is based on public data and I've included deleted posts.

group    N       avg_score bountied_rate accepted_rate 
-------- ------- --------- ------------- ------------- 
before    112270      18.8         0.122         0.123
after     388660       2.9         0.259         0.243
control 26548476       2.3         0.004         0.306

Despite the extra attention, answers posted after the bounty are barely better scored than answers in general. Existing answers get most of the voting benefit of being featured. It seems entirely possible that this is a result of the reward existing answer bounty reason. But new answers are more than twice as likely (26%) to receive a bounty as existing answers (12%).

The odds an answer will be accepted has more to do with the total number of other answers to the question than it's actual quality. So let's look at questions instead:

group  N         avg_score avg_max_score avg_bounties accept_rate avg_views 
-----  --------- --------- ------------- ------------ ----------- --------- 
bounty    161510       2.8          9.45        1.022       0.658      4536
control 14181661       1.5          3.26          N/A       0.572      2242

Questions that have been bountied get higher scoring answers on average. And the highest scoring answer is also markedly higher on average. But as I mentioned above, that could be a function of the greater number of views. There is an increase in accept rate among questions that have been bountied. The surprising thing is how many questions get multiple bounties:

bounties N        answers avg_score avg_max_score accept_rate avg_views 
-------- -------- ------- --------- ------------- ----------- --------- 
 0       14020151     2         1.5           3.2       0.571      2214
 1         158289     3         2.7           8.3       0.659      4269
 2           2979     4.5       5.8          46.1       0.574     14550     
 3            182     7        12.9         189         0.555     48050     
 4             35    10.5      13.5         166.5       0.714     72940     
 5             15     6.1       7.6          25.6       0.467      5346      
 6              4    12        30.8         417.5       0.25     127626    
 7              3    14.7      36.8         392.3       1         96343     
10              1     5        63.8         170         1         46912     
13              1    40        28.4         430         1         67442     
14              1    97       444.2       26940         1       1135600

I venture to guess that a question really isn't getting better answers after it's first bounty. Every measure of quality except accept rate increases with multiple bounties.

Summary

Bounties certainly increase attention (as designed). There is some indication that a single bounty also increases answer quality, but multiple bounties probably don't increase anything but attention. I'm only looking at Stack Overflow, but spot checks other sites show similar results.

Answer 2

Bounties gain attention in their own way on each SE site. Each SE site is a culture of it's own, sometimes with overlap into other SE sites, and sometimes with hardly any overlap at all.

I have offered bounties on a few sites with mixed results:

• On Christianity.SE I have offered a bounty to reward an already existing answer that was quite superb. I earned this one. I have seen, many times, a bounty bring in equally superb answers as many as 100 days after the question was asked.
• On MSE, when it was MSO, actually, I offered a bounty on a feature request that was not my question to get the SE staff to notice it. It received no further attention from anyone except a few more upvotes and a worthless answer that basically said "yep, me too," which three people upvoted for some reason.
• I just offered a bounty on SU for a question that went three weeks with no activity at all. We will see.

On the bigger sites, the quality of interaction seems to decline the bigger it gets. They are a victim of their own success. Hence, I don't think the bounties are too effective for those sites.

On the mid-sized sites, the bounties seem to work very well. There is a high possibility that a regular user can answer very well, but for the few upvotes they might get, they are not really willing to put in the time. The promise of a bounty gives them that extra push.

I have no experience with the small sites, but I suspect the bounties are hit and miss, mostly because there is actually a good chance that none of the regular users can provide a good answer.

See that your only experience is on SO and MSE, I can understand you frustrations.

Here's some examples:

• On C.SE, the bounty made most of those answers; the OP didn't award any of them for some reason: Why does God command us to have children? I personally think most of those answers are pretty good. This question's current bounty brought in three answers so far, of which, one is pretty good. This question's bounty has brought in one answer so far, that at least looks extensive, but I can't comment on quality/factuality; it has no up or down votes.
• On MSE I found my reposting of this, after the bounty on the other did exactly nothing. Still nothing on the reposting: Revisit favorite answers feature request
• This is my question on SU with the current bounty: Is is possible to get a virtual disc drive to mount over usb to another machine's motherboard?

Answer 3

Personally as an answerer, I do get a hit off the dopamine from a bounty - hightened by that delayed gratification and risk while waiting for the bounty to finish. When I put in a good answer but it doesnt get enough votes to score the bounty I am crushed (briefly).

I have several tags where I have expertise but I'll only look at bountied questions. It's an effective way for me to avoid getting too sucked in to SO.

BTW it's so ironic that the OP gave a bounty for the best answer ...