Question: when is the world population expected to reach 8 billion
[{'answer': '2024', 'provenance': [{'wikipedia_id': '19017269', 'title': 'World population', 'start_paragraph_id': 23, 'start_character': 84, 'end_paragraph_id': 23, 'end_character': 88, 'bleu_score': 1.0, 'section': 'Section::::History.:Milestones by the billions.\n'}]}, {'provenance': [{'wikipedia_id': '19017269', 'title': 'World population', 'start_paragraph_id': 23, 'start_character': 0, 'end_paragraph_id': 23, 'end_character': 763, 'bleu_score': 0.956594673454308, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5054543920884689064}, 'section': 'Section::::History.:Milestones by the billions.\n'}]}]