Question: when was vat first introduced in the uk
[{'answer': '1973', 'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 1, 'start_character': 87, 'end_paragraph_id': 1, 'end_character': 91, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 294, 'bleu_score': 0.7496763287404651, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15042660573966622959}, 'section': 'Section::::Abstract.'}]}]