user: Question: Which polling institute has a 30.7% for social democratic?
Columns: ['Date Released', 'Polling institute', 'Socialist', 'Social Democratic', 'Green-Communist', "People's Party", 'Left Bloc', 'Lead']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['October 10, 1999', 'Election Results', '44.1% 115 seats', '32.3% 81 seats', '9.0% 17 seats', '8.3% 15 seats', '2.4% 2 seats', '11.8%']
SQL:

assistant: SELECT "Polling institute" FROM "Table" WHERE "Social Democratic" = '30.7%';