Hello I am trying to transform my wide data (5 countries,3 variables, quarterly data from 1966-2021)into long (panel) but when I try to run the command reshape long GDP CPI REC, i(ID) j(years) ,I get either: variable id does not uniquely identify the observations or variable years contains all missing values. I am really confused because I had approximately the same format in another dataset and reshape worked just fine.
Thank you in advance