user: ### NOW ANSWER:
Question: When was the earliest year that Guillermo Vilas was the runner-up?
Columns: ['Location', 'Year', 'Champion', 'Runner-up', 'Score']
Types: ['text', 'real', 'text', 'text', 'text']
Sample row: ['Lakeway', 1977.0, 'Harold Solomon', 'Ken Rosewall', '7–6, 6–2, 2–6, 0–6, 6–3']
SQL:

assistant: SELECT MIN("Year") FROM "Table" WHERE "Runner-up" = 'Guillermo Vilas';