Question: when did pop music started in what year
[{'answer': 'mid-1950s', 'provenance': [{'wikipedia_id': '24624', 'title': 'Pop music', 'start_paragraph_id': 1, 'start_character': 124, 'end_paragraph_id': 1, 'end_character': 133, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '24624', 'title': 'Pop music', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 428, 'bleu_score': 0.9476990614658231, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6937016823318133670}, 'section': 'Section::::Abstract.'}]}]