Question: when did the federal government switch from csrs to fers
[{'answer': 'January 1 , 1987', 'provenance': [{'wikipedia_id': '1910246', 'title': 'Federal Employees Retirement System', 'start_paragraph_id': 10, 'start_character': 45, 'end_paragraph_id': 10, 'end_character': 61, 'bleu_score': 1.0, 'section': 'Section::::FERS annuity.:Eligibility.\n'}]}, {'provenance': [{'wikipedia_id': '1910246', 'title': 'Federal Employees Retirement System', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 300, 'bleu_score': 0.9569637990759251, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 9722418923617930194}, 'section': 'Section::::Abstract.'}]}]