Stata Panel Data New! -

This is a comprehensive guide to handling, analyzing, and interpreting panel data in Stata. Panel data (also known as longitudinal data) involves observations on multiple cross-sectional units (like individuals, firms, or countries) over multiple time periods.

Handling Lags and Differences

Stata recognizes the panel structure when creating lags or differences, ensuring it does not calculate the difference between two different entities. stata panel data

* Create a lag variable (previous year's value)
gen lag_gdp = L.gdp


Create a difference variable (change from previous year)
gen delta_gdp = D.gdp This is a comprehensive guide to handling, analyzing,


Create a lead variable
gen lead_gdp = F.gdp
 Create a difference variable (change from previous year)

The xtset Command

This is the fundamental command for panel data.

* Basic syntax
xtset panel_id time_variable

Example
xtset country_id year

• panel_id: The variable identifying the cross-sectional unit (e.g., ID, Country, Firm).
• time_variable: The variable identifying the time (e.g., Year, Month).

Marginal Effects after Nonlinear Models:

xtlogit emp wage hours, fe
margins, dydx(*) atmeans

A. Pooled OLS

Treats the data as one big cross-section, ignoring the panel structure.

• Command: reg y x
• Problem: Biased if unobserved individual effects are correlated with independent variables ($Cov(\alpha_i, x_it) \neq 0$). This violates OLS assumptions.