Question: when did vat change from 17.5 to 20
[{'answer': '4 January 2011', 'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 2, 'start_character': 292, 'end_paragraph_id': 2, 'end_character': 306, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 509, 'bleu_score': 0.977897140678983, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10468619598721943070}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'start_paragraph_id': 12, 'start_character': 0, 'end_paragraph_id': 12, 'end_character': 535, 'bleu_score': 0.812825186841413, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 10468619598721943070}, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '34027706', 'title': 'Value-added tax in the United Kingdom', 'section': 'Section::::Abstract.', 'start_paragraph_id': 2, 'end_paragraph_id': 2, 'meta': {'evidence_span': ['There are complex regulations for goods and services imported from "within" the EU. The default VAT rate is the standard rate, 20% since 4 January 2011.', 'he default VAT rate is the standard rate, 20% since 4 January 2011', 'The default VAT rate is the standard rate, 20% since 4 January 2011.']}}]}]