instruction: For those employees who was hired before 2002-06-21, give me the comparison about the average of manager_id over the hire_date bin hire_date by time by a bar chart, and order in descending by the y-axis.
response: SELECT HIRE_DATE, AVG(MANAGER_ID) FROM employees WHERE HIRE_DATE < '2002-06-21' ORDER BY AVG(MANAGER_ID) DESC