user: Question: What year was Best Costume Design the award category?
Columns: ['Year', 'Award', 'Category', 'Nominee', 'Result']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2001.0, 'Tony Award', 'Best Revival of a Musical', 'Best Revival of a Musical', 'Nominated']
SQL:

assistant: SELECT "Year" FROM "Table" WHERE "Category" = 'Best Costume Design';