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Using the Helmert-transformation to reduce dimensionality in a mixed model: An application to a wage equation with worker and firm heterogeneity

A model for matched data with two types of unobserved heterogeneity is considered – one related to the observation unit, the other to units to which the observation units are matched. One or both of the unobserved components are assumed to be random. Applying the Helmert transformation to reduce dimensionality simplifies the computational problem substantially. The framework has many potential applications; we apply it to wage modeling. Traditionally, unobserved individual and firm heterogeneity in wage equations have been represented by fixed effects. However, because of the presence of time-invariant covariates, we argue that specifications with random effects also deserve some attention. Our mixed model allows identification of the effects of time invariant variables on wages, such as for instance education. Using Norwegian manufacturing data it turns out that the assumption with respect to firm-specific unobserved heterogeneity affects the estimate of the return to education considerably.

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Paper provided by Statistics Norway, Research Department in its series Discussion Papers with number 667.

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Date of creation: Oct 2011
Date of revision:
Handle: RePEc:ssb:dispap:667
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  1. M Arellano & O Bover, 1990. "Another Look at the Instrumental Variable Estimation of Error-Components Models," CEP Discussion Papers dp0007, Centre for Economic Performance, LSE.
  2. John M. Abowd & Robert H. Creecy & Francis Kramarz, 2002. "Computing Person and Firm Effects Using Linked Longitudinal Employer-Employee Data," Longitudinal Employer-Household Dynamics Technical Papers 2002-06, Center for Economic Studies, U.S. Census Bureau.
  3. Paulo Guimarães & Pedro Portugal, 2010. "A simple feasible procedure to fit models with high-dimensional fixed effects," Stata Journal, StataCorp LP, vol. 10(4), pages 628-649, December.
  4. Eeckhout, Jan & Kircher, Philipp, 2009. "Identifying Sorting: In Theory," IZA Discussion Papers 4004, Institute for the Study of Labor (IZA).
  5. Vasso Ioannidou & Steven Ongena, 2010. ""Time for a Change": Loan Conditions and Bank Behavior when Firms Switch Banks," Journal of Finance, American Finance Association, vol. 65(5), pages 1847-1877, October.
  6. Biørn, Erik & Godager, Geir, 2009. "Does quality influence choice of general practitioner? An analysis of matched doctor-patient panel data," HERO On line Working Paper Series 2008:3, Oslo University, Health Economics Research Programme.
  7. Robert Plasman & François Rycx & Ilan Tojerow, 2007. "Wage differentials in Belgium: the role of worker and employer characteristics," DULBEA Working Papers 07-12.RS, ULB -- Universite Libre de Bruxelles.
  8. Sónia Torres & Pedro Portugal & John T. Addison & Paulo Guimarães, 2010. "The Sources of Wage Variation: An Analysis Using Matched Employer-Employee Data," Working Papers w201025, Banco de Portugal, Economics and Research Department.
  9. Thierry Lallemand & Robert Plasman & François Rycx, 2005. "Why do large firms pay higher wages? evidence from matched worker-firm data," ULB Institutional Repository 2013/8743, ULB -- Universite Libre de Bruxelles.
  10. Fredrik Heyman, 2007. "Firm Size or Firm Age? The Effect on Wages Using Matched Employer-Employee Data," LABOUR, CEIS, vol. 21(2), pages 237-263, 06.
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