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_name_21 (measurement VARCHAR, estimated_function__percentage INTEGER)
### Question:
What is the measurement where the estimated function % is less than 20?
### Answer:
SELECT measurement FROM table_name_21 WHERE estimated_function__percentage < 20