Talk:Parameter identification problem

The example in the article is more or less consistent with the example at Reduced form; please do not break this consistency.

This includes the use of the symbol M for the number of endogenous variables. See also the motivation for this choice, in the invisible comment in the article where M is introduced. Arie ten Cate (talk) 10:58, 3 February 2008 (UTC)

Note that System of linear equations and Simultaneous equations (in the "See also") overlap much, which might lead to the merging of the two pages (which will then require adaption of the "See also" here).

Arie ten Cate (talk) 21:19, 18 January 2008 (UTC)

The introduction

The addition to the introduction of 1 February 2008 by HyDeckar is useful: in fact, up to that point in time the introduction did not state what the problem was, but only stated in what cirumstances it might occur. (Hence HyDeckar's starting phrase "More generally, ..." is a bit too modest?)

The addition discusses a statistical model, including the expression "the same distribution of observations" (as opposed to simply "the same observations"). However, in the present version of the page, the logic of identification is discussed as simple as possible, without statistics (disturbance terms, probability distribution of the data, etcetera).

Maybe the article must be generalized further by adding after the present discussion a section introducing statistics/stochastics, and thereby linking it better to the discussion of the subject in modern econometrics text?

(In order to make sure that the "more than one equation" in the first sentence of the (old) introduction is not read as having a similar meaning as HyDeckar's "more than one set of parameters which generate the same distribution of observations", I have changed the former somewhat, increasing the precision at the cost of making it slightly more jargon-ish ("multiple equation system"). See my second 3 February 2008 change to the article.)

Arie ten Cate (talk) 10:58, 3 February 2008 (UTC)

Merge with 'identifiability' article

This article describes identifiability in econometrics and economics. There is a separate statistics article called identifiability. Sav8i8 (talk) 11:07, 14 March 2014 (UTC)

Dr. Lippi's comment on this article

Dr. Lippi has reviewed this Wikipedia page, and provided us with the following comments to improve its quality:

Extremely poor. Sloppy references to related use of the term. Instrumental variables are mentioned in "See also" but not in the article. Should be deleted. Maybe professors Hayashi or Fisher might be willing to contribute an article.

We hope Wikipedians on this talk page can take advantage of these comments and improve the quality of the article accordingly.

We believe Dr. Lippi has expertise on the topic of this article, since he has published relevant scholarly research:

• Reference : Forni, Mario & Lippi, Marco & Reichlin, Lucrezia, 2003. "Opening the Black Box: Structural Factor Models versus Structural VARs," CEPR Discussion Papers 4133, C.E.P.R. Discussion Papers.

ExpertIdeasBot (talk) 11:30, 22 December 2016 (UTC)

Article scope and suggested split

This article is based entirely on simultaneous equations models, but the topic is more general (see identifiability). It is unclear to me what this article adds by being standalone. I think the material should be moved to simultaneous equations model, especially the supply-demand example. But some of it might be useful at identifiability as well. Wikiacc (¶) 20:55, 10 August 2020 (UTC)

The mentioned articles are definitely similar but I feel one can make a case for having a standalone article referring to identification of a model in social sciences. First, the identification problem in social sciences also emerges in 1-equation models. In fact, this is more common than the system of equation case. Imagine regressing people's salaries on years of education. How does one know that the estimated effect of higher years of education on salaries is due to the education and not to an innate ability of those people that got their masters degrees? The example with the supply-demand model is just that, an example that happens to be a system of equations. If one has time, this salary example can be written in the article.

Secondly, you can achieve statistical identification without economic (or other social sciences) identification. How come? To achieve statistical identification in the sense of the identifiability article you impose restrictions on your (perhaps system of) equation(s). From a statistical perspective those restrictions should satisfy some conditions and you're done, you achieve statistical identification (i.e, your solution is unique). Now, how does one know that those imposed restrictions to solve the (system of) equation(s) make economic sense? That's economic identification. We say one achieves economic identification when the imposed restrictions make economic sense. Specfifically, they are related to: economic theory or a stylized fact or other empirical confirmation of the phenomena.

Thus, identification of a model in social sciences has statistical identification as a necessary condition (as in the identifiability article) but not sufficient.

Don Ema Valecirro (talk) 02:25, 11 August 2020 (UTC)

@Don Ema Valecirro: Do you have a recent source describing "social sciences identification" as you've put it? The Koopmans article seems to touch on this but the texts on econometrics I can find only discuss statistical identification. Wikiacc (¶) 17:06, 11 August 2020 (UTC)

Lutz KILIAN, LUTKEPOHL Helmut, 2017, Structural vector autorressive analysis in the Introduction of Chapter 14 Identification by heteroskedasticity they emphasize how a model can be identified by heteroskedasticity but those identifying restrictions can fail to have any economic meaning. From the same book, this broad concept of identification is discussed in Chapter 7 A historical perspective on Causal Inference in Macroeconometrics. Sorry, I can't think now of a more broad audience reference than this highly technical book. I will check Peter Kennedy A guide to econometrics. Don Ema Valecirro (talk) 02:17, 12 August 2020 (UTC)

@Don Ema Valecirro: thanks, technical is fine, just needs to clear WP:RS. (As an aside, the article vector autoregression really could use some material on this topic.) I'd note that identification of structural shocks is, at a conceptual level, a pretty different exercise from parameter identification in the supply-demand model on this page, or the Mincer earnings function you described above.

Given the points you raised I now think there's a way to make this article useful as a standalone article. But these points are also reasons why this article needs to be expanded and clarified considerably. Wikiacc (¶) 02:59, 12 August 2020 (UTC)