Question: when did the us stop trading with japan
[{'answer': '1940', 'provenance': [{'wikipedia_id': '13609300', 'title': 'Events leading to the attack on Pearl Harbor', 'start_paragraph_id': 1, 'start_character': 367, 'end_paragraph_id': 1, 'end_character': 371, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': '1939', 'provenance': [{'wikipedia_id': '13609300', 'title': 'Events leading to the attack on Pearl Harbor', 'start_paragraph_id': 8, 'start_character': 175, 'end_paragraph_id': 8, 'end_character': 179, 'bleu_score': 1.0, 'section': 'Section::::Background to conflict.\n'}]}, {'provenance': [{'wikipedia_id': '13609300', 'title': 'Events leading to the attack on Pearl Harbor', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 0, 'bleu_score': 1.0, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10709736396747570356}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '13609300', 'title': 'Events leading to the attack on Pearl Harbor', 'start_paragraph_id': 8, 'start_character': 0, 'end_paragraph_id': 8, 'end_character': 419, 'bleu_score': 0.9699161750394991, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10709736396747570356}, 'section': 'Section::::Background to conflict.\n'}]}, {'provenance': [{'wikipedia_id': '13609300', 'title': 'Events leading to the attack on Pearl Harbor', 'section': 'Section::::Background to conflict.\n', 'start_paragraph_id': 8, 'end_paragraph_id': 8, 'meta': {'evidence_span': ['Beginning in 1938, the U.S. adopted a succession of increasingly restrictive trade restrictions with Japan. This included terminating its 1911 commercial treaty with Japan in 1939, further tightened by the Export Control Act of 1940. These efforts failed to deter Japan from continuing its war in China, or from signing the Tripartite Pact in 1940 with Nazi Germany and Fascist Italy, officially forming the Axis Powers.', 'Beginning in 1938, the U.S. adopted a succession of increasingly restrictive trade restrictions with Japan. This included terminating its 1911 commercial treaty with Japan in 1939, further tightened by the Export Control Act of 1940.', 'Beginning in 1938, the U.S. adopted a succession of increasingly restrictive trade restrictions with Japan. This included terminating its 1911 commercial treaty with Japan in 1939,']}}]}]