Stata handles both gracefully, but you need to be aware of the distinction because estimation methods treat missing data differently.
Generate panel data set obs 630 // 30 countries * 21 years egen country = seq(), from(1) to(30) block(21) bysort country: gen year = 2000 + _n - 1 stata panel data
Before Sam could do anything, he had to tell Stata that his data was special. He used the command: xtset id year This told Stata that was the person and Stata handles both gracefully, but you need to