user: Question: Class of 500cc, and a Wins smaller than 0 had what average year?
Columns: ['Year', 'Class', 'Team', 'Points', 'Wins']
Types: ['real', 'text', 'text', 'real', 'real']
Sample row: [1966.0, '125cc', 'EMC', 2.0, 0.0]
SQL:

assistant: SELECT AVG("Year") FROM "Table" WHERE "Class" = '500cc' AND "Wins" < 0.0;