Question: when was the last time minimum wage was changed
[{'answer': '2015', 'provenance': [{'wikipedia_id': '11477230', 'title': 'Minimum wage in the United States', 'start_paragraph_id': 18, 'start_character': 506, 'end_paragraph_id': 18, 'end_character': 510, 'bleu_score': 1.0, 'section': 'Section::::Legislation.:Living wage protests.\n'}]}, {'provenance': [{'wikipedia_id': '11477230', 'title': 'Minimum wage in the United States', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 571, 'bleu_score': 0.5715187610325, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 4140175430855578929}, 'section': 'Section::::Abstract.'}]}]