How many years has the winner been a member of the National Football League?
CREATE TABLE table_32601 (
    "Year" real,
    "Sportsperson" text,
    "Nationality" text,
    "Team" text,
    "Competition , federation , or league" text,
    "Sport" text
)
SELECT AVG("Year") FROM table_32601 WHERE "Competition , federation , or league" = 'national football league'
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: How many years has the winner been a member of the National Football League? ### Input: CREATE TABLE table_32601 (
    "Year" real,
    "Sportsperson" text,
    "Nationality" text,
    "Team" text,
    "Competition , federation , or league" text,
    "Sport" text
) ### Response: SELECT AVG("Year") FROM table_32601 WHERE "Competition , federation , or league" = 'national football league'