Question: when did the prison population begin to rise dramatically
[{'answer': 'Since 1973', 'provenance': [{'wikipedia_id': '38109642', 'title': 'History of United States prison systems', 'start_paragraph_id': 1, 'start_character': 998, 'end_paragraph_id': 1, 'end_character': 1008, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '38109642', 'title': 'History of United States prison systems', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 1495, 'bleu_score': 0.980856815574177, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3915448499778883443}, 'section': 'Section::::Abstract.'}]}]