What is the average year in which the finish position was 13th?
CREATE TABLE table_63839 (
    "Year" real,
    "Competition" text,
    "Venue" text,
    "Position" text,
    "Notes" text
)
SELECT AVG("Year") FROM table_63839 WHERE "Position" = '13th'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What is the average year in which the finish position was 13th? ### Input: CREATE TABLE table_63839 (
    "Year" real,
    "Competition" text,
    "Venue" text,
    "Position" text,
    "Notes" text
) ### Response: SELECT AVG("Year") FROM table_63839 WHERE "Position" = '13th'