user: Question: How much Standard Rank has a Name of 311 south wacker drive, and a Year larger than 1990?
Columns: ['Pinn. Rank', 'Std. Rank', 'Name', 'Pinnacle height ft (m)', 'Standard height ft (m)', 'Floors', 'Year']
Types: ['real', 'real', 'text', 'text', 'text', 'real', 'real']
Sample row: [1.0, 1.0, 'Willis Tower', '1,730 (527)', '1,451 (442)', 108.0, 1974.0]
SQL:

assistant: SELECT "Std. Rank" FROM "Table" WHERE "Name" = '311 south wacker drive' AND "Year" > 1990.0;