Question: when did houston go 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': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 371, 'bleu_score': 0.9684940092844061, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14332241580695242588}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13894', 'title': 'Houston Astros', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['The Houston Astros are an American professional baseball team based in Houston, Texas. The Astros compete in Major League Baseball (MLB) as a member club of the American League (AL) West division, having moved to the division in 2013', 'The Astros compete in Major League Baseball (MLB) as a member club of the American League (AL) West division, having moved to the division in 2013 after spending their first 51 seasons in the National League (NL).', 'having moved to the division in 2013 after spending their first 51 seasons']}}]}, {'provenance': [{'wikipedia_id': '13894', 'title': 'Houston Astros', 'section': 'Section::::Franchise history.:2010–2014: Last years in the NL and move to the AL West.\n', 'start_paragraph_id': 87, 'end_paragraph_id': 87, 'meta': {'evidence_span': ['the Astros unveiled their new look in preparation for their move to the American League for the 2013 season.', 'On November 2, 2012, the Astros unveiled their new look in preparation for their move to the American League for the 2013 season.', 'the Astros unveiled their new look in preparation for their move to the American League for the 2013 season.']}}]}]