Tyler Cowen reports:

Marginal Revolution: Four new economics journals: The [American Economic] Association will publish four new quarterly refereed journals starting in 2009 that, together, cover the fields of economics... AEJ: Macroeconomics: macroeconomics; monetary economics; international finance; aggregate aspects of development; economic growth; finance; and comparative economic systems. Editor: Olivier Blanchard. AEJ: Microeconomics: microeconomic theory; corporate finance; industrial organization; micro theory aspects of economic development; and micro aspects of international economics. Editor: Andrew Postlewaite. AEJ: Economic Policy: public economics; urban and regional economics; public policy aspects of health, education, and welfare; law and economics; economic regulation; and environmental and natural resource economics. Editor: Esther Duflo. AEJ: Applied Economics: labor; demography; empirical micro development; and health, education, and welfare economics. Editor: Alan Auerbach.

Then I think Tyler becomes confused:

Overall I consider this bad news. It expands the career-making power of one professional association and the editors it nominates. It further encourages overspecialization, and discourages general interest research. It discourages research in the area of whichever journal becomes the weak sister of the four. It makes it harder for an individual piece to stand out as important.

By the time these journals hit the street, it is unlikely that their paper versions will play much of a role at all in deciding what people read--big screens will be too big with too many pixels and printers too fast. What these journals will do is guarantee that Olivier, Andrew, Esther, or Alan is sitting on top of a refereeing process that finds that these papers are interesting. How valuable this signal is depends on how good the editors are at managing referees and how good the editors' tastes are. Certainly AEJ: Macroeconomics and AEJ: Applied Economics will significantly add to my utility. (I don't know Andrew Poslewaite at all, and so don't know how good his taste is, and I have no idea how good a manager Esther will turn out to be.)

Tyler muses further:

The real issue is why articles should be bundled into journals at all...

It used to be a combination of limited economies of scale in distribution and a filtering-signalling mechanism. Now it's overwhelmingly the filtering-signalling mechanism.