Introduction: Why Panel Data Matters in Modern Research In the world of econometrics and data science, not all data is created equal. While cross-sectional data gives you a snapshot in time and time-series data tracks a single entity over time, panel data (also known as longitudinal data) combines both dimensions. It follows multiple individuals, firms, countries, or other units across multiple time periods.
Use pooled OLS as a baseline, but rarely as a final model. Fixed effects removes all time-invariant unobserved heterogeneity by de-meaning the data. It answers: Within a worker, how does changing union status affect wage? stata panel data
xtserial wage experience union Random effects assumes the unobserved panel effects are uncorrelated with your regressors. This is a strong assumption but allows inclusion of time-invariant variables. Introduction: Why Panel Data Matters in Modern Research
Use reshape long to convert to :
xtdpdgmm wage L.wage experience union, gmm(L.wage, lag(2 4)) iv(experience union) : GMM is powerful but complex. Check for overidentifying restrictions with Hansen test after estimation. 4. Fixed Effects with Individual Slopes If effects of time-varying variables differ across panels: Use pooled OLS as a baseline, but rarely as a final model