Question: when did the north american free trade agreement start
[{'answer': 'January 1 , 1994', 'provenance': [{'wikipedia_id': '22050', 'title': 'North American Free Trade Agreement', 'start_paragraph_id': 78, 'start_character': 576, 'end_paragraph_id': 78, 'end_character': 592, 'bleu_score': 1.0, 'section': 'Section::::Disputes and controversies.:Zapatista Uprising in Chiapas, Mexico.\n'}]}, {'provenance': [{'wikipedia_id': '22050', 'title': 'North American Free Trade Agreement', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 334, 'bleu_score': 0.6062264189630721, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2056486881084926850}, 'section': 'Section::::Abstract.'}]}]