Question: when did gst come into effect in canada
[{'answer': 'January 1 , 1991', 'provenance': [{'wikipedia_id': '296406', 'title': 'Goods and services tax (Canada)', 'start_paragraph_id': 16, 'start_character': 51, 'end_paragraph_id': 16, 'end_character': 67, 'bleu_score': 1.0, 'section': 'Section::::Background.\n'}]}, {'provenance': [{'wikipedia_id': '296406', 'title': 'Goods and services tax (Canada)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 481, 'bleu_score': 0.8385073472404351, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5857688500540740978}, 'section': 'Section::::Abstract.'}]}]