Template-type: ReDIF-Paper 1.0 Author-Name: David Hendry Author-Email: david.hendry@nuffield.ox.ac.uk Author-Homepage:http://www.nuff.ox.ac.uk/economics/people/hendry.htm Author-Workplace-Name:Nuffield College, Oxford University Author-Workplace-Homepage:http://www.nuff.ox.ac.uk/nuffield.html Author-Name: Maozu Lu Author-Workplace-Name: Economics Department, Southampton University Author-Name: Grayham E. Mizon Author-Workplace-Name: Economics Department, Southampton University Title: Model Identification and Non-unique Structure Abstract: Identification is an essential attribute of any model's parameters, so we consider its three aspects of 'uniqueness', 'correspondence to reality' and 'interpretability'. Observationally-equivalent over-identified models can co-exist, and are mutually encompassing in the population; correctly-identified models need not correspond to the underlying structure; and may be wrongly interpreted. That a given model is over-identified with all over-identifying restrictions valid (even asymptotically) is insufficient to demonstrate that it is a unique representation. Moreover, structre (as invariance under extended information) need not be identifiable. We consider the role of structural breaks to discriminate between such representations. Length:16 pages Creation-Date: 2001-05-01 Number:2002-W10 File-URL:http://www.nuff.ox.ac.uk/economics/papers/2002/w10/DEISTGEM.pdf File-Format: application/pdf Handle: RePEc:nuf:econwp:0210