Interviewer instructions
The year the establishment began operation refers to the year in which the establishment actually started producing (or providing services), not to the year in which it was registered for the first time. The answer is independent of ownership at the time.
If the establishment was privatized, then the date provided should refer to when the original government-owned establishment began operations.
If the establishment changed its production significantly to change sector classification, then the year when that took place should be provided.