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_19948664_2 (index__year_ VARCHAR, world_ranking__1_ VARCHAR)
### Question:
How many years were recorded when world ranking was 21st?
### Answer:
SELECT COUNT(index__year_) FROM table_19948664_2 WHERE world_ranking__1_ = "21st"