How about the nature of the variables (issue of causality) included in your model?

Have a look at

Article Fixed and Random effects models: making an informed choice

and

Article Explaining Fixed Effects: Random Effects Modeling of Time-Se...

and

https://en.wikipedia.org/wiki/Kelvyn_Jones

under academic controversies - fixed versus random

Dear AKHTER

1. Some right models are suggested above.

2. Several new techniques are developed in this topic. Examples are:

· Empirical strategies to deal with unbalanced panel data

· Stochastic frontier functions with unbalanced panel

· bias-corrected least-squares dummy variable (LSDV) estimators and their bootstrap variance–covariance matrix

3. References:

· Studenmund , A. H.(2014). Using Econometrics: A Practical Guide. Pearson.

· Kennedy, Peter (2008). A Guide to Econometrics. The MIT Press

Cambridge, Massachusetts.

· Kazuhiko Hayakawa & Minoru Nogimori(2010).New transformation methods in dynamic panel data models with heterogeneous time trends. Journal

· Applied Economics Letters , Volume 17, Issue 4, pages 375-379. https://doi.org/10.1080/13504850701735831

· MOHAMED GOAÏED and RYM BEN AYED-MOUELHI (2000).

Efficiency Measurement With Unbalanced Panel Data: Evidence from Tunisian Textile, Clothing and Leather Industries. Journal of Productivity Analysis

Vol. 13, No. 3 (May 2000), pp. 249-262

https://www.jstor.org/stable/41770018

· Changyong FENG, Hongyue WANG, Naiji LU, Tian CHEN,1 Hua HE, Ying LU, and Xin M. TU (2014). Log-transformation and its implications for data analysis. Shanghai Arch Psychiatry. Apr; 26(2): 105–109.

· doi: 10.3969/j.issn.1002-0829.2014.02.009

· https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120293/

· Christopher F Baum (2013).Panel data management, estimation and forecasting. https://www.birmingham.ac.uk/Documents/college-social-sciences/business/economics/kit-baum-workshops/Bham13P3slides.pdf

· Badi H. Baltagi (20 ).Panel Data Methods

· http://zinc.zew.de/pub/zew-docs/sws/baltagi.pdf

· Josef Brüder (2015). Applied Panel Data Analysis Using Stata. https://www.ls3.soziologie.uni-muenchen.de/studium-lehre/archiv/teaching-marterials/panelanalysis-bruederl.pdf

· Seppo Pynn¨onen (2018). Econometrics II

· http://lipas.uwasa.fi/~sjp/Teaching/ecmii/lectures/ecmiic2.pdf

· TomWansbeek (1992).Transformations for panel data when the disturbances are autocorrelated. Structural Change and Economic Dynamics, Volume 3, Issue 2, December 1992, Pages 375-384. https://www.sciencedirect.com/science/article/pii/0954349X9290013V

Regards,

Zuhair