Question: when did large numbers of african-americans first leave the south
[{'answer': 'between 1916 and 1970', 'provenance': [{'wikipedia_id': '375540', 'title': 'Great Migration (African American)', 'start_paragraph_id': 1, 'start_character': 238, 'end_paragraph_id': 1, 'end_character': 259, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '375540', 'title': 'Great Migration (African American)', 'start_paragraph_id': 1, 'start_character': 70, 'end_paragraph_id': 1, 'end_character': 903, 'bleu_score': 0.769900252627664, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6408745942800640797}, 'section': 'Section::::Abstract.'}]}]