In establishing the Problems and Solutions (P&S) series of Econometric Theory, the primary objective was pedagogical—to provide an intellectual resource for students, instructors, and researchers through the publication of student exercises and research-level problems in econometrics. Over the past 20 years, the P&S series has successfully served this goal. Large numbers of worked exercises and problems have now been published, and the series has promoted interaction between problem solvers, problem posers, and the ET readership, thereby helping to bring the wider econometric community together in a common purpose.

The general objectives of the series remain valid today. Yet, there seem to be good reasons for changing the publication format of the series, particularly in view of advances in electronic communication. Readers may now engage in immediate discussion of issues arising from published work the moment it appears online or in the journal. So the built-in publication delay between the setting of a problem in one issue and the provision of a solution in a later issue now seems unnecessary and somewhat artificial. It also seems appropriate to confine ourselves to electronic submissions so that we can expedite processing and publication. Over the years many of our colleagues have suggested improvements to the format of the P&S series and we appreciate the interest and input of our readers in this Series. With the many suggestions we have received, we have designed a new series that we hope will appeal to our readers.

Starting with the first issue in 2005 of ET (Vol. 21:1), we are implementing a new format for the P&S series. Problems and solutions are now to be published together in the form of a short paper or note, complete with the author's name and affiliation just as in the regular publication of an article. Accordingly, we are changing the title of the series to “Notes and Problems” (NP). Each paper in the new NP series will be a self-contained complete publication of a worked exercise or a research-level problem. Readers are invited to contribute different solutions for the problem, to be published one year later, again as a self-contained note. As always, proposed additional solutions will be selected on the basis of the correctness, conciseness, generality, elegance, and diversity of methods employed. Notes outlining interesting unsolved problems will still be welcome.

We hope this change will be attractive to our readers and encourage many new submissions. Note that submissions are now only electronic; please submit papers intended for the NP Series to et@eco.uninsubria.it. NP papers should have a clear title, the author(s) name and affiliation(s), no abstract, and unnumbered sections that follow the suggested format: “Motivation and Results,” “Proofs and Discussion,” and “References.” Additional material may be placed in a technical appendix. Following the publication of an NP paper, comments and alternative solutions may be submitted and should be self-contained (only a brief outline of the problem is necessary). Submission of all papers intended for the NP series should include both a PDF file and all the source files derived from any TeX program (LaTeX, Scientific Word, Plain TeX, AMS TeX), including graphics files.

March 2004