On modeling heterogeneity in linear models using trend polynomials

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Author(s)
Michaelides, Michael
Spanos, Aris
Date Issued
March 18, 2019
Abstract
The primary aim of the paper is to consider the problems and issues raised when the data exhibit time heterogeneity in the context of linear models. Ignoring time heterogeneity will undermine the reliability of inference and will give rise to untrustworthy evidence. Accounting for it using trend polynomials, however, is non-trivial because it raises several modeling issues. First, when the degree of the polynomial is greater than 4, or so, one needs to deal with the near-multicollinearity problem that arises. The second issue pertains to the type of polynomial that will adequately account for the time heterogeneity. Third, when the trend polynomials are treated as additional regressors, they will give rise to highly misleading statistical results. The paper investigates how different types of polynomials could deal with the near-multicollinearity and the modeling issues they raise, and makes recommendations to practitioners.
Journal
Economic Modelling
Department
Economics
Citation
Michaelides, M., & Spanos, A. (2020). On modeling heterogeneity in linear models using trend polynomials doi:https://doi.org/10.1016/j.econmod.2019.05.008
Publisher
Elsevier
Version of Article
Final manuscript post peer review, without publisher's formatting or copy editing (postprint)
Embargo
This version of the article is available for viewing to the public after May 18, 2022.
DOI
10.1016/j.econmod.2019.05.008
ISSN
1873-6122
Rights
This is an open access article distributed under the terms of the Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) Creative Commons license.
Subjects

Linear model

t-Hererogeneity

Near-collinearity

Trend polynomial

Orthogonal polynomial...

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