Question: what caused the areas of the united states to nearly double between 1800 and 1810
[{'answer': 'high birth rate', 'provenance': [{'wikipedia_id': '1610496', 'title': 'Economic history of the United States', 'start_paragraph_id': 8, 'start_character': 565, 'end_paragraph_id': 8, 'end_character': 580, 'bleu_score': 1.0, 'section': 'Section::::Colonial economy to 1780s.:Demographics.\n'}]}, {'answer': 'availability of cheap land', 'provenance': [{'wikipedia_id': '1610496', 'title': 'Economic history of the United States', 'start_paragraph_id': 85, 'start_character': 206, 'end_paragraph_id': 85, 'end_character': 232, 'bleu_score': 1.0, 'section': 'Section::::Early 19th century.:Agriculture, commerce and industry.:Population growth.\n'}]}, {'provenance': [{'wikipedia_id': '1610496', 'title': 'Economic history of the United States', 'start_paragraph_id': 85, 'start_character': 0, 'end_paragraph_id': 85, 'end_character': 536, 'bleu_score': 0.977397480575333, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 13922028996050110769}, 'section': 'Section::::Early 19th century.:Agriculture, commerce and industry.:Population growth.\n'}]}]