Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Class of 500cc, and a Wins smaller than 0 had what average year?

### Inputs:
table_name: table, columns: ['Year', 'Class', 'Team', 'Points', 'Wins']

### Response:
SELECT AVG Year FROM table WHERE Class = 500cc AND Wins < 0