How to find out the average duration of the peer-review process for a given journal?
For publishing in mathematics you could check out the AMS' Backlog of Mathematics Research Journals. Among other things it provides a current estimate of waiting time between submission and publication and historical data for the time between submission and final acceptance.
I'd personally take these estimates with a grain of salt, but I suppose if you're desperate it's better than nothing.
n.b. I think this answer is more relevant outside of mathematics, which is the OP's field ...
Although @Thomas's answer is correct that most journals to which you could submit your paper will be sharing the same reviewer pool, there can be big differences between journals in how efficiently their editorial processes run and, importantly, how much they pressure authors to return reviews quickly.
- You can look on a journal's web page to see if they give any metrics, or emphasize speed: for example, Nature Communications says in their Aims and Scope section:
We are committed to providing an efficient service for both authors and readers. Our team of independent editors make rapid and fair publication decisions.
Obviously that doesn't give you anything hard and fast, but it does at least tell you that they prioritize speed.
- As I've mentioned in a previous question about rapid peer review, SciRev is a web site that is attempting to gather and collate journal-specific information about the peer review process, including processing times. (Unfortunately it hasn't reached a tipping point of popularity yet, so it may not actually provide much useful information.)
someone has done an analysis of publication delays based on data from PubMed (Zenodo repository here). The linked blog post has a dynamic graphic window that lets you select specific journals, but some caveats:
- the data are a bit out of date by now (up to 2015)
- PubMed has good coverage only for biomedical and related journals
- not all journals post the necessary metadata (submission and acceptance dates)
- resetting due to "reject and resubmit" can skew the values
The other point I made in my previous answer about rapid peer review is that depending on your situation, it might not be as important as you think to have your paper published; in many cases, submission to a reputable journal counts for almost as much as publication - it indicates to potential admissions committees, employers, etc. that your work is actually ready for prime time (as opposed to "in prep", which can mean anything from "I've got a good idea" to "submitting tomorrow"). Depending on journal policies etc. within your field, you could also consider posting your paper to a pre-print service such as ArXiv - another way of convincing people that your work is for real.
The best way to figure out the true importance of rapid publication for your situation is probably to talk to a senior colleague in your field who knows your situation.
This is more of a comment, but it needs to be said:
The length of the peer review process depends on the reviewers. If the reviewers are slow, there is little the journal can do about it beyond some reminder emails.
Ultimately, all the journals will be asking the same set of people to review your paper. So don't expect that one journal will really be much faster than another.
Conferences can present a faster publication route because they have a schedule to keep. However, reviewing speed often comes at the cost of quality.