Question: when did the houston astros switch to the american league
[{'answer': '2013', 'provenance': [{'wikipedia_id': '13894', 'title': 'Houston Astros', 'start_paragraph_id': 1, 'start_character': 229, 'end_paragraph_id': 1, 'end_character': 233, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13894', 'title': 'Houston Astros', 'start_paragraph_id': 85, 'start_character': 0, 'end_paragraph_id': 85, 'end_character': 758, 'bleu_score': 0.9853469949554711, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14695812212843879772}, 'section': 'Section::::Franchise history.:2010–2014: Last years in the NL and move to the AL West.\n'}]}]