Publishing similar/same paper twice? (regarding Economics Letters journal) I've always been under the impression that you're only allowed to publish 1 result in 1 journal. However, Economics Letters states:


  For instance, a theorist could submit to Economics Letters a
  thought-provoking example before the analysis is extended to a general theorem in a fully fledged paper that will go elsewhere. Similarly, an experimentalist or an empirical researcher could submit to Economics Letters some important preliminary results, where perhaps the threshold for robustness, thoroughness or completeness of the analysis is not as high as it would be for a complete paper.


Is this stating that you're allowed to submit early results of paper X to Economics Letters, then improve paper X until paper X is longer and more like a full paper, followed by a submission of paper X to an alternative journal? If it is what they mean, why don't more academics do this to boost their publication count? Economics Letters is actually ranked quite highly.
Taken from the comments as per request

This is fairly common. For example, in CS, one might publish preliminary work at a conference, and then flesh it out for a journal (there's a "30% new material" rule in many journals to cover this situation). But to answer your question, doing this doesn't boost publication count except for very dumb ways of evaluating a publication list. Most people (except university bureaucrats) will list the conference and journal paper as one entity.

Note that it is upto the journal editors of the second venue to decide whether the paper is sufficiently different from the first one. They are free to reject it even if you think the latter paper is a nontrivially expanded version of the first one.