user: Question: What is the average age as of February 1, 2014 for the supercentenarians born in the United States?
Columns: ['Name', 'Birth date', 'Age as of 1 February 2014', 'Province or Country of birth', 'Province of residence']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Merle Barwis', '23 December 1900', '113years, 40days', 'United States', 'British Columbia']
SQL:

assistant: SELECT AVG("Age as of 1 February 2014") FROM "Table" WHERE "Province or Country of birth" = 'United States';