Question: when did penn st join the big ten
[{'answer': '1990', 'provenance': [{'wikipedia_id': '78358', 'title': 'Big Ten Conference', 'start_paragraph_id': 4, 'start_character': 346, 'end_paragraph_id': 4, 'end_character': 350, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '78358', 'title': 'Big Ten Conference', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 751, 'bleu_score': 0.8970019490239041, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11724637861567037327}, 'section': 'Section::::Abstract.'}]}]