Publishing similar/same paper twice? (regarding Economics Letters journal)
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.