Question: when was the uk national minimum wage introduced
[{'answer': '1998', 'provenance': [{'wikipedia_id': '1127188', 'title': 'National Minimum Wage Act 1998', 'start_paragraph_id': 0, 'start_character': 26, 'end_paragraph_id': 0, 'end_character': 30, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]