Panel data

Summary

• A cross-sectional sample of individuals (individuals, firms, etc.) observed over time is called a panel data set .
• \(y_{i,t}\) denotes the observation of individual \(i\) at time \(t\) of the dependent variable.
• \(x_{i,t,j}\) denotes the observation of individual \(i\) at time \(t\) of explanatory variable \(j\) .
• There are \(n\) individuals, \(i=1,…,n\) and \(T\) time periods, \(t=1,…,T\) .
• If data exists for every individual at every time period, we say that the panel is balanced . Otherwise it is unbalanced.