Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_103084_4 (year VARCHAR, bbc_one_rank VARCHAR)
### Question:
How many years did BBC One rank 20th?
### Answer:
SELECT COUNT(year) FROM table_103084_4 WHERE bbc_one_rank = "20th"