The unit of analysis is the couple, meaning that each line corresponds to a couple.
However, some specifications should be considered:
Wave 1 - couple (both partners were interviewed)
Wave 2 - couple (only the female partner from the original couple of wave 1 was interviewed)
Wave 3 - couple (several situations: both partners of the original couple, only one partner of the original couple, new partner of the original couple, both partners from the cohort refreshment in wave 3)
