The average length of an economics paper (1.5-spacing, 12-point font, and 1-inch margins) grew from 16 pages in the early 1970s to 45.5 pages in 2011–12, a nearly 300 percent increase (see this Card and DellaVigna article in the Journal of Economic Literature for more details or this Vox summary of the article). That said, as David Evans puts it in a recent blog entry: "Good ideas don’t have to be long ideas." So where should we send shorter papers? Should we bother writing them at all? Read David Evans blog for the official statistics, but I will emphasize that it really depends on (1) how fast you can write the short paper, (2) whether it's even possible to write a longer paper with existing data, and (3) whether the short paper would make an important contribution to the literature.
If you do decide that a short paper makes sense, look here for ideas about where to send it. As you can see in the comments, the Review of Economics and Statistics also sometimes publishes short papers. You may also be able to submit papers for possible inclusion in the American Economic Review Papers and Proceedings issue by submitting your paper to the AEA Meetings. In fact, if you submit to a CSWEP session, your changes may be a bit higher.
Or you can just wait a while. Word on the street is that there may be a brand new journal in the works for short papers....let's see what happens.
