For Formulas generated by build_..._couple functions, always use for output_period the year starting 1 year before the beginning of the month.
For Formulas generated by build_..._couple functions, always use for output_period the year starting 1 year before the beginning of the month.

benjello/openfisca-core,openfisca/openfisca-core,adrienpacifico/openfisca-core,openfisca/openfisca-core,benjello/openfisca-core,sgmap/openfisca-core